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MEMCAL    ^SCHOOL 
UIBMAHrif 


ti 


CHEMICAL  AND  PHARMACEUTIC 


MANIPULATIONS. 


»,  »     t  ■> 


CHEMICAL  AND  PHARMACEUTIC 

MANIPULATIONS: 


A  MANUAL  OF  THE  MECHANICAL  AND  CHEMICO-MECHANICAL 
»  OPERATIONS  OF  THE  LABORATORY, 

CONTAINING 

A  COMPLETE  DESCR^TION  OF  THE  MOST  APPROVED  APPARATUS,  WITH 

INSTRUCTIONS  AS  TO  THEIR  APPLICATION  AND 

MANAGEMENT  BOTH  IN 

MANUFACTURING  PJIOCESSES, 

AND  IN  THE  MORE  EXACT  DETAILS  *0F 

ANALYSIS  AND  ACCURATE  RESEARCH.  - 

FO^  THE  USE  OP  CHEMISTS,  DRUGGISTS,  TEACHERS  AND  STUDENTS. 


BY 

CAMPBELL    M^O  REIT, 

PRACTICAL  AND  ANALYTIC  CHEMIST,  AUTHOR ^F  "APPLIED  CHEMISTRY,"  ETC. 

ASSISTED  BY 
ALEXANDER    MUCKL6, 

CHEMICAL  ASSISTANT  IN  PROFESSOR  BOOTH'S  LABORATORY. 


WITH  FOUR  HUNDRED  AND  TWENTY-THREE  ILLUSTRATIONS. 


1^ 


PHILADELPHIA: 

LINDSAY    AND    BLAKISTON, 
1849. 


"The   Hou»e  tUat   Jauk  BuUt.'» 

One  of  the  beat  travesties  on  the  old  nursery  tal^ 

the  full  iwirig  froGa  au  exchange:  _ 

he  White  House— This  is  the  house  thHi'Samj 

built.  .   ■  "!i>^v^  '■■  .■     .    i;  '^■ 

LOO. OUO -This  is  the  malt  that  lay  m  t^ehoaee 

thut  S^mhuilt.  '       •  v.  '■'- 

ames  Buchan^u— This  is  the  rat  that  ate  the  malt, 

thai  lay  iu  the  house  tliat  Sam  built: 
.  A.  Douglas— Thw  is  the  cat  thnt  killed  the  rat. 

that  Hte  the  malt,  that  lay  in  the  house  that 

Sara  t'uih.  . 

ireckiiiridpe— This  is  the  dog,  that  worried  the 

cat,  that  killed  the  rat,  that  ate  the  malt,.thftt; 

lay  iu  ihe  house  th it  Sam  biiilt. 
lell-Bverett—  rhia  is  the  c  )w  with  the  crumpled 

horn,  that  tossed  the  d.-g,  that  worried  the 

cat,  et'% 
fewYoik  Bxrreps— This  is  the  maiden,  all  forn 

lorn,  that  mi.ked  the  cow  with  the  crumpled 

horn,  that,  etc. 
ournal  of  Commerce— This  is  the   man,  all  tat- 
tered  and  torn,  that  kissed  the  itaiden,  all 

forlorn,  that,  etc. 
Jew  York  Onserver— This  is  the  prie«t,  a!F  shaven 

and  shoru,  that  married  the  man,  all  fntterod 

arjd  t  fTQ,  unto  'he  aiaid^n  all  for 
ndependent— Tliis  i-  the  cock  that  r 

morn,  to  waken   the  priest    mI'  :;  _:_ 

shorn,  that  married  them-  td  aud 

torn,  etc.  .  ■  ^ 

Lbe  Lincohi— This  is  the    hun-  •   --.-,* 

and  imin,  that  owned  the  • 

the  morn,  to  waken  the  pri' 

shorn,  I  hit  m  lined  the  m.i 

torn,  uuu)  ihe  maiden  all  t 

the  cow  witii  a  crumbled  li 

dog,  that  w.  rried  the  cat, 

that  ate  the  malt,  that  la} 

Sam  huilt. 

I.  B,*a  Farewell    to   tl&«    lV||^lte    House. 

I^arewell  to  the  land  where  tihe  gloom  of  my  glory. 
Arose  and    o'ershaduwed   the   earth  with  her 
name  ; 
}he  abandous  me  now,  but  the  page  of  her  story, 

The  foulest  aud  blackest,  Uflil'd  with  my  shame. 
!  have  war'd  with  the  Yankees,  who  vanquished 
me  only 
When  th-.  scent  of  the  "  da;\  .  d  to  his 

lair ; 
[have  coped  with  the  free  who  dt^iii-c  me'*ihu8 
loMe'y, 
The  last  tiaJtorous  "  Doughface"  who'll  sit  in 
this  chair.  Jf. 


OUR  PUBLIC  SCHOOLS. 


[The  following  beautiful  song,  by  Mrs.  C.  H. 
GiLDERSLEEVE,  was  sung  at  the  late  Teachers' 
Convention  at  Buffalo.] 

A  song,  a  song  for  public  schools, 

Our  people's  proudest  glory, 
And  while  we  sing,  the  nation's  stars 

Grow  brighter  at  the  story,     • 
And  lighter  float  those  restless  folds. 

And  higher  still  we  follow; 
And  scorn  a  name  whose  only  sound, 

Like  ringing  gold,  is  hollow. 

Then  free  as  air  shall. kflowl edge  be, 

And  open  window's  portals, 
To  every  thirsty,  earnest  soul, 

Who  longs  to  be  immortal. 
Here  rich  and  poor  stand  side  by  side 

To  quaff  her  poorest  chalice, 
And  neverdream  that  deathless  names 

Belong  to  cot  or  palace. 

The  light  of  truth  shall  guide  us  on, 

When  glory  lies  before  us, 
And  "Right  makes  Might"  emblazoned  on 
''    The  banner  waving  oe'r  us. 
iA  song,  a  loud,  exultant  song 

Shall  ring  from  sea  to  prairie, 
And  tell  the  world  that  mikd  not  gold, 

Shall  make  our  stations  vary. 


Lincoln's  Majoeity,,in  New  .Yobk.— Thej 
Tribune  of  the  12th  foots  up  Lincoln's  majopv^ 
ty  in  that  State  about  51,777.  The  rural  dis-' 
trlcls  loom  up.  St.  Lawrence  Co.  gives  7,214 
Republican  mnjority  !  j 


MARRIED. 

On  January  3rd,  1861,  by  Rev.  S.  Searls 
at  the  residence  of  the  bride's  father,  in  Dart- 
ford,  Dr.  H.  L.  Baenes  and  Miss  Nelly  E. 
Cody,  all  of  Dartford,  Wis. 


LAnELPHIA : 

J.  COLLINS,  PRINTERS. 


BY  OLIVEE  WENDELL  HOLMES. 


6?  2)6/ 

A184 

/849 


3  count  the  broken  lyrevS  that  rest, 

Where  the  sweet  wailing  singers  slumber, 

it  o'er  their  silent  sister's  breast 

rbe  wild  flowers  who  will  stop  to  number  ? 

few  can  touch  the  magic  string, 

(Vnd  noisy  Fame  is  proud  to  win  them ; 

IS  !  for  those  that  never  sing; 

3ut  die  with  all  their  music  in  them  ! 

y,  grieve  not  for  the  dead  alone 

^' hose  song  has  told  their  heart's  sad  story- 

ep  for  the  voiceless,  who  have  known 

>ie  cross  witiii>ut  the  crown  of  glory  !  . 

where  Leucadian  breezes  sweep 
>'er  Sappho's  memory-haaoted  pillow,  I  ' 

where  the  glistening  night-dews  weep 

''er  nameless  sorrow's  church  yard  pillow,  ^.        #.  i  i  -i  ^  ^^  .- 

•^  V^        stic  01  modern  philosophy, — distin- 

learts  that  break  and  give-np^slsn      ^       j^t  system,  the  futility  of  which  is 

I ve  whitening  lips  and  fading  tresses,  L  ,     .  ■■  .  i     • 

Death  pours  out  his  cordial  wine.      [;ses_pstract  speculations  upon  whlch   it 

ow-dropped  from  Misery's  crushing  pres. -3  principles  are  Supported  by  facts 

nging  breath  or  echoing  chord 

)  every  hidden  pang  w^re  given,    '        '  ^ 


EFACE. 


riment. 


t  endless  melodies  were  poured, 
i  sad  as  earthy  as  sweet  as  heaven  ! 


f  reasoning,  which  has  led  to  gi- 
parted  to  chemistry  all  its  consist- 
'  ^nue,  ife'thfe'Oril^r'Siire  way  of  .pursuing  investigation,  for  it  is 
by  conclusions,  and  not  hypotheses,  that  we  can  show  the  com- 
position of  bodies,  or  the  principles  which  govern  their  re- 
actions. 

To  realize,  therefore,  for  chemistry  the  simple  definition  of 
a  science, — to  render  it  "a  system  illustrated  and  proved  by 
experiment,"  it  is  requisite  for  us  to  acquire  some  proficiency 
in  those  mechanical  operations  by  means  of  which  chemical 
changes  are  produced,  observed  and  estimated. 

This  accomplishment  in  manipulation, — this  expertness  in 
handling  implements,  it  is  true,  demands  practice  and  expe- 
rience ;  but  though  the  student  cannot  become  an  adept  in  the 
art  solely  by  the  aid  of  written  directions,  yet  much  may  be 
communicated  which  will  lighten  labor  and  facilitate  him  in 
the  attainment  of  skill  and  accuracy. 


^41^0 


VI  PREFACE. 

Such  has  been  the  author's  object  in  preparing  the  present 
work,  which  in  its  arrangement  is  designed  to  lead  the  unin- 
itiated step  by  step  into  the  mysteries  of  manipulations;  and 
in  which  he  has  endeavored  with  less  regard  to  elegance  of  ' 
diction  than  to  perspicuity,  to  present  plainly  and  clearly 
such  information  as  is  best  calculated  to  give  familiarity  with 
the  construction,  arrangement  and  uses  of  apparatus. 

Positive  originality  can  scarcely  be  expected  in  any  ac- 
count of  the  well  known  appliances  of  the  chemical  art.  The 
author  has,  however,  while  availing  himself  freely  of  the 
knowledge  of  others,  endeavored  to  combine  with  it,  as  much 
as  possible,  personal  experience,  and  to  present  descriptions 
of  new  and  important  forms  of  apparatus,  with  practical 
suggestions  of  a  novel  character. 

In  confessing  indebtedness  to  other  chemists,  the  author 
acknowledges  his  obligations  to  Prof.  J.  B.  Reynolds  for  the 
whole  of  the  chapter  upon  "Analysis  by  Polarization  of 
Light,"  a  subject  which  the  writer's  skill  and  experience 
have  well  qualified  him  to  illustrate. 


CONTENTS.  Xlll 


CHAPTER  XXVII. 

BLOWPIPE  MAWIPULATipir. 

Use  and  construction  of  blowpipes.  Wollaston's,  Gahn's,  Mitscherlich's 
blowpipes.  Economical  blowpipe.  Blowpipe  lamp  and  appliances. 
Flame.  The  mode  of  holding  the  blowpipe  : — the  blast ; — the  supports. 
Detection  of  volatile  substances  by  means  of  the  blowpipe.  Instruments 
used  in  analyses  by  the  blowpipe.  Reagents.  Blowpipe  table.  The 
test  series  .  .  .  .  .  .  .  .  367 


CHAPTER  XXVIII. 

AlfALTSIS  OF  SACCHAHINE  SUBSTANCES   BY  PGLARTZATIOTT  OF  LIGHT. 

The  polarizer  and  analyzer ; — circular  polarization.  Ventzke's  apparatus. 
Method  of  analyzing  sugars.  Decolorization  of  colored  solutions.  Soleil's 
saccharimeter.  Clerget's  method.  Table  for  the  analysis  of  saccharine 
substances  .  .  .  .  .  .  .  .391 


CHAPTER  XXX. 

ELECTRICITY. 

Electrical  machines  5  Leyden  jar ; — electrical  battery ; — discharger.  The 
electrophorus.  Detection  and  measurement  of  .  electricity ;  —  Henly's 
quadrant  electrometer  ; — Bennet's  and  Coulomb's  electrometers.  Appli- 
cations of  electricity: — eudiometry;  —  Ure's  eudiometer.  Galvanism. 
Wollaston's,  Daniell's,  Smee's,  Grove's,  and  Bunsen's  batteries  : — con- 
nection of  batteries.  Electrolysis.  Production  of  heat  and  light  by  gal- 
vanism. Hare's  sliding  rod  eudiometer  and  calorimotor.  The  means 
of  detecting  galvanic  fluid ; — the  galvanometer.     Astatic  galvanometer   .  409 


CHAPTER  XXXI. 

CONSTRUCTION  OF  FORMULA  .  .  .   452 


XIV  CONTENTS. 


CHAPTER  XXXII. 


GLASS-BLOWIJfG. 


Blowpipe  table  and  lamp:  —  Implements.  Cutting  of  glass.  Tubes 
cemented,  bent,  drawn  out,  and  closed.  Lateral  attachments.  Bulbs 
blown.     Welter's  and  funnel  tubes  fashioned       .  .  .  .455 


CHAPTER  XXXni. 

CORKS. 

Corks  softened, — perforated.     Cork  borer    .....  466 

CHAPTER  XXXIV. 
dealehs  in  and  manufacturers  of  apparatus     .  .  468 


^^s 


THE  LABORATORY. 


CHAPTER   I. 


The  Laboratory  is  emphatically  the  work-shop  of  the  che- 
mical operative ;  and  chemical  manipulation  may  be  termed 
the  practice  of  the  science.  A  convenient  arrangement  of 
the  first  is  no  less  desirable,  for  the  success  of  operations,  than 
a  proficiency  and  skill  in  the  latter  is  indispensable.  New 
facts  in  science  are  mainly  developed  by  experiment ;  and  as 
chemistry  is  a  purely  experimental  science,  in  every  course  of 
research,  as  well  in  the  most  ordinary  experiments  as  in  the 
more  delicate  manipulations  of  analyses,  the  surest  basis  of 
accurate  conclusions  is  an  exact  and  skilful  manipulation 
coupled  with  correct  reasoning.  This  exemplification,  by 
the  hands,  of  the  conceptions  of  the  mind,  is,  therefore,  an 
art  of  the  highest  importance  in  the  pursuit  of  chemistry. 

The  laboratory  should  be  appropriately  fitted,  and  arranged 
with  a  view  to  the  easy  prosecution  of  chemical  investiga- 
tion in  all  its  several  branches ;  and  being  the  place  where 
most  of  the  operator's  time  is  so  profitably  and  pleasantly 
employed,  no  little  regard,  in  its  appointments,  should  also 
be  given  to  personal  comfort  and  convenience.  We  do  not 
recommend  extravagance  in  its  furniture  and  paraphernalia, 
or  yet  a  too  rigid  economy,  for  though  a  stinted  apparatus 
'^^y?  hy  ingenuity  and  skill,  be  rendered  subservient  to  the 
requirements  of  the  science,  a  liberal  endowment  is  far  pre- 
ferable, and  more  conducive  to  rapidity  of  progress  and  accu- 
racy of  results.  In  the  present  advanced  state  of  the  mechanic 
arts,  it  is  doubtful  economy  to  consume  time  in  constructing 
contrivances,  when  the  most  convenient  apparatus  may  be 
readily  procured  at  the  lowest  rates.  Moreover,  a  familiarity 
with  the  use  of  good  tools  originates  habits  of  correct  and 
3 


56  LIGHT — VENTILATION. 

delicate  manipulation,  and  will  afford,  to  the  experimenter, 
a  proficiency  enabling  him,  in  any  emergency,  to  substitute 
available  material  for  deficient  apparatus;  whilst  in  working 
upon  rare  substances,  the  minutest  quantity  will  be  no  bar  to 
his  skill  and  accuracy  in  bringing  out  nice  results. 

We  do  not,  in  the  following  suggestions,  provide  for  such  a 
laboratory  as  is  suitable  for  a  public  institution,  because  the 
adaptation  of  one  of  that  extent  would  be  attended  with  an 
expense  inconsistent  with  individual  means,  as  there  are  many 
auxiliaries  required  in  class  experiments  which  may  readily  be 
dispensed  with  in  an  ordinary  laboratory;  but,  we  present  an 
apartment  economically  and  conveniently  arranged  for  private 
research,  with  space  and  furniture  enough,  with  some  slight 
multiplication  of  the  apparatus,  for  two,  four,  or  more  ex- 
perimenters. 

In  the  construction  of  a  laboratory,  particular  attention 
should  be  paid  to  the  lighting  and  ventilation  of  the  apartments, 
both  in  regard  to  the  health  and  comfort  of  its  occupants. 
The  preferable  mode  of  lighting  is  by  side  windows,  and  for 
many  reasons;  it  is  more  advantageous  in  examining  the 
behavior  of  re-agents  to  solution,  especially  in  those  instances 
of  delicate  testing,  where  the  result  is  determinable  by  the  form- 
ation of  flocculae,  faint  cloudiness,  or  by  slight  transmutation 
of  color.  By  elongating  the  windows  to  nearly  the  whole  height 
of  the  apartment,  we  obtain  the  magic  influence  of  the  solar 
rays,  now  known  to  be  so  effective  in  inducing  chemical 
changes  unattainable  by  other  means.  The  skylight  arrange- 
ment has  the  double  disadvantage  of  presenting  nuclei  for  the 
accumulation  of  dust,  and  being  subject  to  frequent  breaches 
by  accident  or  storm.  Ventilation  may  be  accomplished 
thoroughly  by  means  of  counterpoised  windows  and  stationary 
hoods. 

The  laboratory  apartment  should  be  sufficiently  spacious 
to  afford  a  separate  position  for  each  of  the  requisite  utensils. 
Too  much  crowding  of  apparatus  engenders  liability  of  damage, 
and  is,  besides,  inconvenient,  for  nowhere  than  in  a  laboratory 
is  there  more  necessity  of  a  strict  observance  of  the  rule,  "a 
jplace  for  everything ^  and  everything  in  its  place.''  Hunting 
up  mislaid  apparatus  consumes  time,  and  the  delay  thus  oc- 
casioned, in  many  instances,  may  be  the  means  of  serious 
detriment  to  important  operations. 

A  roomy  apartment  on  the  first  floor  of  a  building  is  best 


-VS-fjiv^-iiSSiip., 


.■•x»:*»*i»w*- 


^t'K^toaJC 


':^!^^^^'^mw^mm 


THE  FURNACE.  35 

ratus,  to  keep  the  side  door  i  (7  feet  high,  and  2.10  wide)  lead- 
ing into  the  main  apartment  constantly  closed.  The  front  of 
this  wing  is,  as  to  windows,  identical  with  that  of  the  office. 
The  free  admission  of  light,  which  is  effected  by  means  of  the 
two  long  front  and  three  elevated  side  windows,  is  as  requisite 
in  this  as  in  the  operating  room.  The  chimney  of  this  apart- 
ment occupies  the  centre  of  the  outer  wall,  and  receives  the 
main  flue,  furnishing  draft  to  the  main  furnace  and  two  late- 
ral branches.  Of  these  two  branch  flues,  both  of  which  have 
circular  openings  with  movable  tin  stopples,  one  is  for  the 
reception  of  the  smoke-pipe  of  the  still  furnace  E,  and  the  other 
for  that  of  the  steam  generator  F ;  or,  when  not  in  use  other- 
wise, for  the  portable,  blast,  and  other  furnaces.  These  flues 
are  fitted  with  dampers  to  regulate  the  draught;  and  the  cir- 
cular opening,  when  not  occupied  with  apparatus,  or  as  vent 
holes  for  the  dispersion  of  noxious  vapors,  should  be  kept  co- 
vered so  as  to  preserve  unimpaired  the  draught  of  the  main 
furnace.  In  the  arrangement  of  a  room,  for  laboratory  pur- 
poses, wherein  the  flues  are  not  convenient,  they  must  be  sub- 
stituted by  stove-pipes. 

The  Furnace. — The  furnace  Gr,  which  is  in  constant  use  for 
the  ordinary  operations  of  the  laboratory,  occupies  the  centre 
of  the  outer  wall.  That  of  most  convenient  construction  is 
described  by  Faraday,  to  whom  we  are  indebted  for  both  our 
description  and  figures. 

"Being  in  constant  requisition  as  a  table,  it  should  be  about 
34  or  35  inches  in  height.  The  brick  work  should  measure 
36  by  20  inches,  and  the  iron  plate,  including  sand-baths,  40 
by  28  inches.  A  warm  air  chamber  may  be  built  in  the  walls 
beneath  the  flue.  Projecting  spikes  should  be  fastened  into 
one  or  two  sides  of  this  chamber,  to  hold  a  temporary  shelf 
when  required. 

"Precipitates,  filters,  and  other  moist  substances  put  into 
such  a  chamber,  are  readily  and  safely  dried.  The  hot  air 
causes  evaporation  of  the  water,  whilst  the  current  removes 
the  rising  vapor.  The  chamber  is  very  useful  in  effecting  the 
slow  evaporation  of  liquids,  and  also  for  hot  filtrations,  when 
the  entering  current  of  air  is  of  a  temperature  sufficient  for 
the  purpose. 

"The  principal  part  of  this  furnace  is  necessarily  of  brick- 
work, only  the  top  plate  with  the  baths  and  the  front,  being 
of  iron.  The  front  is  a  curved  iron  plate,  having  two  aper- 
tures closed  by  iron  doors,  one  belonging  to  the  fire-place,  and 


THE  FURXACE. 


Fig.  6. 


the  other  to  the  ash-pit.     It  is  34  inches  high,  and  14  inches 
wide.     The  ash-hole  door  moves  over  the  flooring  beneath ; 

the  bottom  of  the  fire-place 
door  is  22  inches  from  the 
ground,  and  the  door  itself 
is  8  J  inches  bj  7.  This  front 
is  guarded  within  at  the  part 
which  encloses  the  fire  by  a 
strong  cast-iron  plate,  having 
an  opening  through  it  corre- 
sponding to  the  door  of  the 
fire-place.  It  has  clamps 
attached  to  it,  which,  when 
the  furnace  is  built  up,  are 
enclosed  in  the  brick-work. 
In  the  setting  or  building  of  the  furnace,  two  lateral  brick 
walls  arc  raised  on  each  side  the  front  plate,  and  a  back  wall 
at  such  a  distance  from  it  as  to  leave  space  for  the  ash-hole 
and  fire-place ;  these  walls  are  lined  with  Welch  lumps,  where 
they  form  the  fire-chamber;  two  iron  bars  are  inserted  in  the 
course  of  the  work  to  support  the  loose  grate  bars  in  the  usual 
manner,  the  grate  being  raised  19  inches  from  the  ground. 
The  side  walls  are  continued  until  of  the  height  of  the  front, 
and  are  carried  backward  from  the  front  in  two  parallel  lines, 
so  as  to  afford  support  for  the  iron  plate  which  is  to  cover  the 
whole.  The  back  wall  of  the  fire-place  is  not  raised  so  high 
as  the  side  walls  by  six  inches  and  a  half,  the  interval  which 
is  left  between  it  and  the  bottom  of  the  sand-bath,  being  the 
commencement  of  the  flue  or  throat  of  the  furnace.  In  this 
way  the  fire-place,  which  is  fourteen  inches  from  back  to  front, 
and  nine  inches  wide,  is  formed,  and  also  the  two  sides  of  the 
portion  of  horizontal  flue  which  belongs  to  the  furnace,  and 
is  intended  to  heat  the  larger  sand-bath.  The  bottom  of  this 
part  of  the  flue  may  be  made  of  brick- work,  resting  upon  bear- 
ers laid  on  the  two  side  walls,  or  it  may  be  a  plate  of  cast-iron 
resting  upon  a  ledge  of  the  brick-work  on  each  side,  and  on 
the  top  of  the  wall,  which  forms  the  back  of  the  fire-place. 
When  such  an  arrangement  is  adopted,  the  plate  must  not  be 
built  into  the  brick-word,  but  suffered  to  lie  on  the  ledges, 
which  are  to  be  made  flat  and  true  for  the  purpose ;  for,  if 
attached  to  the  walls,  it  will,  by  alternate  expansion  and  con- 
traction, disturb  and  throw  them  down.     The  ends  of  the  side 


THE  FURNACE. 


87 


walls,  forming  as  it  were  the  back  of  the  furnace,  may  be 
finished  either  by  being  carried  to  the  wall  against  which  the 
furnace  is  built,  or  enclosed  by  a  piece  of  connecting  brick- 
work, to  make  the  whole  square  and  complete,  or  a  warm  air 
cupboard  may  be  built  in  the  cavity  beneath  the  flue,  and  the 
door  made  to  occupy  the  opening  between  the  walls.  Occa- 
sionally the  flue  may  be  required  to  descend  there,  and  pass 
some  distance  under  ground.  These  points  should  be  arranged 
and  prepared  before  the  plate  constituting  the  top  of  the  fur- 
nace is  put  on  to  the  brick-work,  so  that  when  the  plate  with 
its  sand-baths  are  in  their  places,  they  may  complete  the  por- 
tion of  horizontal  flue  by  forming  its  upper  side. 

The  size  of  this  plate  is  the  first  thing  to  be  considered,  and 
having  been  determined  upon,  from  a  consideration  of  the 
situation  to  be  occupied  by  the  furnace,  and  the  places  of  the 
sand-baths  also  having  been  arranged;  the  brick-work  must 
then  be  carried  up,  so  as  to  correspond  with  these  determina- 
tions, and  with  the  plate  itself,  which  in  the  mean  time  is  to 
be  cast.  The  sand-baths  and  the  plate  are  to  be  formed  in 
separate  pieces.  The  bath  over  the  fire  is  best  of  a  circular 
form,  and  of  such  diameter  that,  when  lifted  out  of  its  place, 
it  may  leave  an  aperture  in  the  plate  equal  in  width  to  the 
upper  part  of  the  fire-place  beneath ;  so  that  a  still,  or 
cast-iron  pot,  or  a  set  of  rings  may  be  put  into  its  place  over 
the  fire.  The  other  sand-bath  must  be  of  such  a  form  as  to 
correspond  with  the  shape  and  size  of  the  flue  beneath.  These 
vessels  are  to  be  of  cast-iron,  about  three-tenths  of  an  inch 
thick;  their  depth  is  to  be 
two  inches  and  a   half  or  ^^*  ' 

three  inches,  and  they  are 
to  be  cast  with  flanches,  so 
as  to  rest  in  the  correspond- 
ing depressions  of  the  plate 
that  the  level  of  the  junc- 
tions may  be  uniform.  This 
will  be  understood  from  the 
accompanying  section  of  the 
furnace,  given  through  the 
line  AB  of  the  view.  It  is  essential  that  these  sand-baths 
be  of  such  dimensions  as  to  fit  very  loosely  into  the  apertures 
in  the  plate,  when  cold,  a  space  of  the  eighth  of  an  inch  or 
more  being  feft  all  round  them,  as  shown  in  the  section,  other- 


38 


THE  FURNACE — THE  SAND  BATHS. 


wise,  when  heated,  they  will  expand  so  much  as  entirely  to 
fill  the  apertures,  and  even  break  the  plate.  The  plate  itself 
should  be  half  an  inch  thick. 

When  the  plate  and  its  sand-baths  are  prepared,  and  the 
brick-work  is  ready,  the  furnace  is  finished  by  laying  the  plate 
on  the  brick-work,  with  a  bed  of  mortar  intervening.  If  the 
walls  are  thin,  or  any  peculiarity  in  their  arrangement  occa- 
sions weakness,  they  should  be  bound  together,  within  by 
cranks  built  into  the  work,  and  without  by  iron  bands.*  The 
alternate  changes  of  temperature  from  high  to  low,  and  low 
to  high,  to  which  the  furnace  is  constantly  subject,  renders  it 
liable  to  mechanical  injury,  in  a  degree  much  surpassing  that 
which  would  occur  to  a  similar  piece  of  brick-work,  always 
retained  nearly  at  one  temperature."  The  square  space  en- 
closed by  the  fire-place  and  flues  may  be  converted  into  ail 
excellent  drying  or  warm  air  chamber  if  desired. 

Cast-iron  is  the  best  material  for  these  baths,  for,  though 
liable  to  be  cracked  when  first  heated,  by  their  unequal  ex- 
pansion in  diff*erent  parts,  they  do  not  warp  and  assume  the 
irregular  and  inconvenient  shapes  that  wrought  iron  acquires 
under  similar  circumstances. 

"  These  baths  should  have  washed  sea-sand  put  into  them ;  it 
is  heavy,  and  occasions  no  dust  when  moved,  whilst,  on  the 
contrary,  unwashed  and  bad  sand  contains  much  dirt,  and 
occasions  great  injury  in  experimenting.  A  piece  of  straight- 
ened iron  hoop,  about  twelve  inches  in  length,  should  lie  on 
the  furnace,  as  an  accompaniment  to  the  baths,  being  a  sort  of 
coarse  spatula  with  which  to  move  away  the  sand. 

The  circular  sand-bath  is  frequently  replaced  by  a  set  of 
concentric  iron  rings,  or  a  cast-iron 
pot.  The  rings  are  convenient  for 
leaving  an  aperture  over  the  fire  of 
larger  or  smaller  dimension,  according 
as  a  smaller  or  larger  number  are  used 
at  once;  and  being  bevelled  at  the 
edges,  fit  accurately  into  each  other, 
without  any  risk  of  becoming  fixed  by 
expansion.  The  external  one,  like  the 
sand-baths,  should  be  made  smaller 
than  the  depression  in  the  furnace 
plate  in  which  it  rests.  The  iron  pots 
are  of  various  sizes,  and  are  adapted 


Fig.  8. 


THE  FURNACE — THE  SAND  BATHS.  39 

to  the  furnace  by  means  of  the  rings ;  a  red  heat  is  easily 
obtained  in  them  for  sublimation." 

In  m^ny  instances,  where  economy  is  of  prime  importance, 
the  foregoing  sand-bath  can  in  a  measure  be  substituted  by 
an  ordinary  cylinder  stove,  the  pipe  of  which  leading  into 
a  four  sided  sheet  iron  box,  divided  into  flues  by  par- 
titions, imparts  its  heat  which  eventually  passes  into  the 
chimney.  The  top  of  this  box  when  covered  with  sand,  forms 
the  sand-bath.  That  portion  of  its  surface  immediately  over 
the  first  flue,  is  the  hottest.  The  remote  or  cooler  end,  is  best 
adapted  for  gradual  digestions,  evaporations,  &c.;  and  so  by 
these  flues  there  is  a  means  of  graduating  the  temperature  of 
the  bath.  The  top  of  the  stove  itself  being  directly  over  the 
fire,  makes  an  excellent  bath  for  those  operations  requiring  a 
higher  temperature. 

This  arrangement,  or  the  still  more  economical  gas  bath 
(Fig.  27)  described  at  p.  48,  renders  necessary  the  use  of 
Luhme's  or  Kent's  portable  furnace  for  fusions,  crucible  or 
other  operations  requiring  a  very  high  heat,  but  this  involves 
no  additional  expense,  for  such  an  implement  is  indispensable 
for  other  laboratory  purposes. 

The  steam  generator  (Fig.  10)  when  used  as  a  stove  for 
heating  the  apartment,  answers  equally  well  to  heat  the  bath, 
it  being  only  necessary  to  conduct  its  smoke-pipe  into  the 
iron  box  instead  of  leading  it  directly  into  the  chimney. 

To  prevent  contamination  of  the  atmosphere  of  the  apart- 
ment, by  admixture  with  the  deleterious  fumes  evolved  dur- 
ing the  various  operations  of  digestion,  fusing,  melting,  heat- 
ing, and  evaporating  in  progress  upon  the  sand-bath  and  in 
the  furnaces,  there  should  be  firmly  fastened  to  the  ceiling 
and  immediately  over  its  surface,  extending  beyond  its 
superficies  some  four  inches  all  around,  a  sheet-iron  hood,  of 
form  at  the  base  corresponding  with  that  of  the  top  of  the 
furnace.  The  barrel  of  this  hood  may  pass  either  directly 
through  the  ceiling  and  roof  into  the  atmosphere,*  or  else  be 

*  When  the  external  atmosphere  is  colder  than  that  within,  an  air-vent  over- 
head does  not  thoroughly  relieve  the  room  of  its  noxious  vapors,  for  the  cold  air 
rushing  in  depresses  them, — even  within  the  sphere  of  respiration,  and  thus 
prevents  their  ascent  and  consequent  escape  through  the  hoods.  Dr.  Murray's 
very  simple  and  effectual  plan  of  ventilation,  is  to  conduct  a  funnel-mouthed 
pipe  through  the  ceiling  into  a  chimney  where  a  constant  fire  is  maintained. 
To  provide  against  the  entrance  of  smoke  by  reason  of  imperfection  of  draught, 


40 


THE  FURNACE — THE  HOOD. 


formed  into  an  elbow,  leading  into  the  main  flue  of  the  chim- 
ney. In  either  case  the  draft  must  be  thorough,  so  as  to  afford 
a  free  egress  of  the  fumes  into  the  atmosphere  without.     It 

should  also  be  immovably 
Fig.  9.  fixed  by  rod  iron  stretch- 

ers, and  well  payed  over 
with  plumbago  paint,  which 
is  a  resistant  of  the  corro- 
sive effect  of  the  lalToratory 
fumes,  and  thus  prevents 
the  destruction  of  the  me- 
tal. The  fixture  is  repre- 
sented by  Fig.  9.  It  should 
descend  as  near  to  the  sur- 
face of  the  bath  as  conve- 
nience of  manipulation  will 
allow ;  and  to  prevent  any 
accumulation  of  dirt  in  the 
interior,  it  should  be  fre- 
quently brushed  out  with  a 
soft  brush  ;  and  for  protection  to  the  vessels  on  the  sand-bath, 
against  falling  particles,  the  top  of  the  furnace  should,  during 
the  operation,  be  covered  with  paper.  It  is  advisable  at  all 
times,  independently  of  the  foregoing  suggestion,  to  keep  each 
vessel  covered  with  plates  or  clean  white  paper,  which,  while 
protecting  against  dirt,  offers  no  impediment  to  the  processes 
of  evaporation,  digestion,  &c.  If  the  hood,  instead  of  being 
fixed  is  counterpoised,  so  as  to  admit  of  ready  depression  or 
elevation  at  will,  it  is  a  little  more  convenient ;  but  that  arrange- 
ment has  the  disadvantage  of  liability  to  accident,  for  a  care- 
lessness in  fastening  the  suspension  cords  may  create  a  very 
annoying  damage.  Of  course,  this  mode  of  hanging  the  hood 
can  only  be  adopted  where  the  barrel  or  pipe  is  straight,  and 
leads  directly  through  the  roof;  then  to  protect  the  exit  hole 
from  the  wear  and  tear  consequent  upon  the  abrasion  of  its  cir- 
cumference, it  should  be  fitted  with  an  earthen  ware  cylinder'; 
and  furthermore,  to  prevent  the  entrance  of  rain  through  the 


the  pipe  should  be  carried  to  the  top  of  the  chimney.  The  uniformly  high 
temperature  of  the  chimney  keeps  the  pipe  constantly  hot,  and  thus  the 
mephitic  vapors  within  the  room  will  be  disengaged.  By  arranging  the  barrel 
of  the  hood  as  thus  directed,  an  equally  effectual  disengagement  of  vapors  may 
be  obtained. 


THE  LABORATORY — THE  STEAM  GENERATOR. 


41 


Fig.  10. 


slight  openings,  there  should  be  a  spreading  flange  around 
the  protruding  portions  of  the  barrel  of  the  hood,  near  the 
roof. 

The  Steam  Generator. — To  the  right  of  the  furnace,  at  a 
convenient  distance,  is  the  portable  steam  generator  F,  with  its 
smoke  pipe  leading  into  the  circular  opening  of  the  lateral 
flue  opposite.  This  is  a  patent  invention  by  C.  W.  Bently, 
of  Baltimore,  Md.  It  has  a  stove-like  form,  is  compact,  re- 
quires no  brick  work  and  but  very  little  fuel,  and  can  be 
set  up  and  removed  at  will,  when  it  is  desired  to  occupy 
the  flue  with  other  apparatus.  The 
only  fixtures  requisite,  in  addition  to 
the  machine,  are  feed  pipes  to  con- 
vey the  water,  and  conduits  for  the 
passage  of  the  steam.  It  is  a  most 
convenient  apparatus  for  the  labora- 
tory, being  alike  handy  for  econo- 
mically supplying  hot  water  to  all 
parts  of  the  building,  and  for  boiling 
substances,  where  the  direct  admis- 
sion of  steam  is  preferable ;  and 
also  for  heating  the  steam  baths  in 
the  range  a  little  to  its  left.  This 
mode  of  applying  heat,  having  the 
great  advantages  of  safety,  conve- 
nience and  regularity,  is  absolutely 
requisite  in  many  cases  where  the 
naked  fire  does  not  ofi'erthat  uniform- 
ity of  temperature  necessary  to  the 
inalterability  of  certain  substances 
under  process.  Fig.  10  represents 
the  apparatus.  By  means  of  cou- 
pling screws  and  flexible  lead  pipe, 
(Tatham's  most  preferable,  being 
smooth  within,)  the  steam  may  be 
carried  to  any  reasonable  distance  in  any  direction,  thus 
affording  great  facility  in  many  operations;  as  the  loss  by 
condensation  in  thus  conveying  it  is  inconsiderable.  In  very 
cold  apartments,  however,  when  the  conduit  pipe  is  of  any 
great  length,  it  may  very  properly  be  enveloped  with  woolen 
listing  or  other  bad  conducting  materials.  Unless  this  ma- 
chine is  kept  in  constant  use  as  a  heater  for  the  building  and 
4 


42 


THE  LABORATORY — THE  STEAM-BATHS. 


the  sand  bath,  as  suggested  at  page  31,  wood  is  the  more 
preferable  fuel,  as  it  admits  of  ready  ignition,  and  enables  a 
speedier  generation  of  the  steam  than  could  be  obtained  with 
coal.  The  lower  cock  in  the  figure  connects  with  the  feed 
pipe.  The  three  smaller  cocks  above,  and  placed  equi-distant 
from  each  other,  are  try  cocks,  to  ascertain  the  height  of  the 
water,  by  which  its  supply  must  be  accordingly  regulated. 
The  steam  conduits  are  coupled  by  a  cock  fitted  to  the  top 
of  the  generator. 

The  door  in  the  lower  part  is  for  the  introduction  of  fuel 
into  the  fire  hole. 

Steam-baths. — Immediately  to  the  right  of  the  generator, 
and  affixed  against  the  back  wall  of  the  room,  as  at  1 1,  plate 
2,  are  the  steam-baths,  mounted  in  a  wooden  frame  work  (Fig. 
11).  Two  or  three  are  as  many  as  necessity  calls  for  in 
the  laboratory.  They  are  of  copper,  and  double  bottomed ; 
the  inner  jacket  of  one  may  be  of  smooth  copper,  and  the  other 
of  tinned  copper  or  sheet  lead.  The  larger  of  the  two  may 
have  a  diameter  of  thirteen  inches  and  a  depth  of  twenty 
inches,  the  smaller  being  each  way  five  inches  less  in  size. 
Fig.  11  represents  the  apparatus.     There  can   be  a   third, 


Fig.  11. 


with  very  little  additional  expense  of  money  or  room,  and  this 
should  have  its  inner  jacket  of  thin  cast  iron  with  porcelain 
lining,  as  being  more  suitable  for  those  operations  which  are 
corrosive  of  metallic  vessels.     These  latter  are  made  to  order 


THE  LABORATORY — THE  STILL.  43 

by  Savery,  the  former  by  Hammet  and  Hiles,  of  Philadelphia. 
The  outer  jackets  h  h  h  are  invariably  of  copper. 

Immediately  over  the  frame  work,  which  is  stationary, 
resting  and  fastened  against  the  back  wall,  is  a  welded  wrought 
iron  steam  conduit  B^  forming  the  main  feeder  for  the  baths 
a  a  a.  The  supply  of  steam,  which  is  conveyed  to  each  through 
a  pipe  c?,  connected  with  the  main  feeder  and  fastened  to  the 
back  of  the  outer  jacket  5,  is  regulated  by  the  cocks/  and  c. 
The  safety  valves  are  supported  by  uprights  e  e  e^  firmly  fixed 
to  the  floor  beneath.  The  stop  cocks  ccc  render  each  kettle 
independent  of  the  others,  so  that  the  use  of  one  does  not  ne- 
cessarily compel  all  to  be  in  operation. 

This  apparatus  is  very  convenient  for  exhausting  vegetable 
matters,  such  as  dye  woods,  plants,  &c.,  of  their  matter  solu- 
ble in  water,  and  whose  active  principles  are  liable  to  be 
damaged  by  fire.  The  saving  in  fuel  and  time,  the  perfect 
freedom  from  waste  steam,  the  power  of  regulating  the  heat, 
are  only  a  few  of  the  advantages  of  this  mode  of  boiling  over 
the  old  plan  of  heating  in  open  kettles  over  the  naked  fire. 

Moreover,  when  the  exhaustion  is  complete,  the  heat  may 
be  discontinued  by  merely  stopping  off  the  steam  with  the 
cock  c.  By  another  connection  with  the  hydrant,  enabling  a 
current  of  fresh  water  as  soon  as  the  steam  is  turned  off,  the 
apparatus  is  converted  into  a  refrigerant,  and  its  contents  may 
be  cooled  as  suddenly  as  desired. 

Near  to  the  steam  series,  are  two  steaming  cisterns  of 
an  half-barrel  capacity  each.  One  may  be  of  deal  or  oak 
wood  and  iron  bound,  the  other  of  blue  stone-ware,  from  the 
Baltimore  pottery.  These  tanks  are  mounted  upon  pedes- 
tals, and  being  readily  handled  for  filling,  emptying,  and 
cleansing,  are  very  convenient  for  those  operations  where  the 
direct  application  of  steam  is  necessary.  A  flexible  leaden 
pipe  from  the  main  conduit,  leads  the  steam  directly  into  the 
vessels,  and  produces  a  uniform  ebullition.  The  form  of  these 
tanks  is  similar  to  that  of  butter  or  meat  tubs.  To  prevent 
the  diffusion  of  the  steam  through  the  apartment,  the  vessels 
must  be  kept  covered  during  the  operations  of  boiling. 

The  Still. — On  the  left  of  the  furnace,  as  at  E  H,  PI.  2,  and 
occupying  the  same  relative  position  there  as  the  generator  on 
its  right,  are  the  still  and  refrigerant,  which  are  indispensable 
utensils,  both  for  a  supply  of  pure  water  for  analyses,  &c.,  and 
for  the  many  distillatory  operations  connected  with  chemical 


44 


THE  LABORATORY — THE  STILL. 


research.  In  its  construction  there  should  be  particular  regard 
to  compactness,  so  that  the  implement  may  combine  the  double 
advantage  of  a  naked  and  water  bath  still.  For  convenience 
and  economy  of  room,  we  prefer  that  this  apparatus  be  mova- 
ble, and  therefore  recommend,  as  a  substitute  for  a  brick  wall 
bed  or  setting,  a  portable  stove-like  cylinder  of  thick  sheet 
iron.  The  fire  door  is  as  shown  in  the  figures  below,  and  in 
order  to  prevent  the  overheating  of  the  iron  cylinder,  the  part 
which  contains  the  fire  should  be  lined  with  a  refractory  earthen 
cylinder,  of  about  two  inches  thickness,  as  at  h  and  c,  in  Fig. 
12.  The  smoke  pipe  leads  into  the  circular  opening  of  the  op- 
posite flue.  The  body  of 
Fig.  12.  the  still  rests  upon  the  rim 

of  this  furnace  at  a,  by  its 
flange,  which  surrounds  it 
immediately  below  its  han- 
dles. It  is  shown  by  (7, 
Fig.  13.  Its  dimensions 
should  be  so  much  less  than 
those  of  the  furnace,  as 
to  leave  sufficient  heating 
space  around  its  sides  and 
bottom.  The  material  of 
the  still  is  copper,  and  the 
joints  are  rounded  so  as  to  give  every  facility  in  cleansing. 
Moreover,  round  edges  are  less  liable  to  become  bruised  than 


NAAAAMAl 


^ 


iz> 


^ 


Fig.  13. 


Fig.  14. 


~^ 

t      B 

1 
1 

1 

I'S- 

J 

THE  LABORATORY — THE  STILL.  45 

the  angular.  For  the  distillation  of  substances  indestructible 
at  high  temperatures,  this  still  is  applicable  over  the  naked 
fire,  but  for  more  alterable  bodies,  the  intervention  of  water  is 
necessary,  and  so,  accordingly,  an  inner. tinned  copper  or  ena- 
meled iron  jacket  is  provided.  The  form  and  position  of  this 
jacket  are  shown  at  B^  by  the  dotted  lines  in  Fig.  13.  It  is  a 
straight  cylinder  with  convex  bottom,  and  a  broad  rim,  serving 
also  as  a  flange  or  rim  for  its  support  in  the  still.  Its  dimen- 
sions are  four  inches  in  diameter  and  eight  inches  in  depth  less 
than  those  of  the  still.  The  head  or  capital,  which  should  be  of 
tinned  copper,  or,  preferably,  of  pewter,  is  shown  at  A,  The 
rim  is  made  to  fit  the  mouth  of  either  the  still  or  water  bath, 
and  hence  the  same  head  answers  in  both  naked  and  bath  dis- 
tillations. The  beak  conveys  the  vapors  accumulating  in  the 
capital,  into  the  refrigerant  or  condenser,  which  consists  of  a 
pewter  worm  Fig.  14,  encased  in  a  wooden  tub  kept  con- 
stantly supplied  with  cool  water  through  the  pipe  e.  The 
water  pipe  which  carries  off  the  heated  water  displaced  by  the 
cold  water,  runs  from  the  top  of  the  tub,  and  has  its  exit 
into  the  sink,  or  through  the  wall,  into  the  gutter.  These 
two  pipes  are  better  of  lead.  The  vapors  in  passing  through 
the  worm  are  condensed  and  drop  as  a  liquid  into  a  receiver, 
which  is  placed  beneath  the  outlet  pipe  near  the  bottom  of  the 
tub. 

To  convert  the  apparatus  into  a  water  bath,  (for  in  many 
distillations  the  temperature  must  not  exceed  the  foiling  point 
of  water  or  a  saline  solution,)  it  is  only  necessary  to  charge 
the  outer  jacket,  or  still,  with  the  proper  quantity  of  liquid, 
and  then  to  insert  the  inner  casing  jB,  which  slides  into  the 
mouth  and  fits  tightly. 

In  the  distillation  of  flowers,  roots,  and  other  substances, 
in   the  naked  still,  a  too  close  contact  with  its  heated  sides 
and  bottom  renders  them  liable  to  injury  by  scorching,  and 
therefore  it  is  necessary  to  have  a  strong  wire 
stand  with  one  or  two  cullendered  shelves  upon  ^^^-  ^^^ 

which  to  place  the  material.  The  lower  shelf 
h  being  an  inch  or  two  from  the  bottom  of 
still,  prevents  all  liability  of  contact  between 
it  and  the  material.  This  apparatus  is  shown 
by  Fig.  15.  When  the  still  is  not  in  use  for 
its  legitimate  purpose,  by  removal  of  the  wire 


46 


THE  LABORATOEY — THE  STILL. 


shelving,  it  becomes  an  excellent  kettle  for  any  of  the  ordinary 
boiling  operations. 

In  the  blank  space  of  the  wall  to  the  left  of  the  front 
entrance,  stands  a  deal  wood  cask,  with  wooden  spigot, 
mounted  upon  a  stand  of  convenient  height.  This  serves 
as  a  reservoir  for  distilled  water,  and  the  opening  for  pour- 
ing in  the  water  must  be  kept  tightly  closed  to  prevent  the 
admission  of  dust  or  absorption  of  gases. 

The  Sink. — In  the  corner  of  the  room  to  the  right  of  the 
refrigerant,  is  the  sink.  Its  position  will  be  better  understood 
by  reference  to  I,  PI.  2.  As  it  is  necessary  that  the  labora- 
tory should  be  abundantly  and  constantly  supplied  with  water 
for  cleansing,  distilling,  -and  many  other  operations,  it  is 
better  in  those  cities  where  the  water  is  supplied  by  public 
water-works,  to  make  an  attachment  to  the  main  conduit,  and 
lead  the  water  through  a  lead  pipe  directly  into  the  laboratory, 
and  immediately  over  the  sink.  The  only  arrangement  ne- 
cessary is  a  stop-cock  at  the  termination  of  the  pipe,  to  regu- 
late the  flow  of  water.  Fig.  16  represents  a  sink  thus 
arranged.  The  trough  should  be  of  wood  and  lined  with 
sheet  lead,  which  metal  is  preferable 
to  zinc ;  because  less  liable  to  corrosion 
by  acids,  for  the  formation  of  holes, 
by  amalgamation  with  mercury,  can 
be  avoided  with  a  little  care  in  washing 
vessels  containing  residua  of  it,  or  the 
solutions  of  its  salts.  The  floor  be- 
neath, to  a  certain  extent  around  the 
sink,  should  also  be  covered  with  sheet 
lead,  otherwise  its  continual  dampness 
from  the  splashing  water  would  endan- 
ger the  health  of  the  operator.  When 
the  introduction  of  water  by  conduit 
is  impossible,  it  is  necessary  to  erect 
immediately  over  the  sink  a  strong 
iron-bound  oaken  reservoir  with  cover, 
which  must  be  daily  filled  with  buckets 
from  the  neighboring  pump.  In  either 
case,  the  exit-cock  should  be  fitted  with  one  of  Jennison's 
filters,  a  small  metallic  casing,  Fig.  17,  containing  a  stratum  of 
crushed  quartz,  which  arrests  the  suspended  impurities  of  the 
water  during  its  percolation  through.     If  it  is  not  convenient 


Fig.  16. 


THE  LABORATORY — THE  STILL. 


47 


to  provide  one  of  the  above  filters,  an  economi-  Fig.  17. 

cal,  but  slower  and  less  convenient  one  can 
be  made  of  a  common  red  earthenware  flower- 
pot by  covering  its  bottom  interiorly  with  a 
linen  cloth  and  filling  it  with  coarse  white  sand. 
The  waste-pipe,  which  must  be  constructed  so 
as  to  admit  of  the  free  egress  of  the  waste-water, 
into  a  drain  which  conveys  its  charge  into  cess-pools  or  tanks 
lined  with  brick,  and  sunk  into  the  ground.  As  the  emana- 
tions of  foul  air  from  these  pools  are  noxious,  they  should  be 
placed  some  distance  from  the  building,  and  kept  well  covered. 
If  the  situation  be  favorable,  the  drains  should  empty  them- 
selves into  a  gutter  or  some  running  stream,  which,  in  con- 
ducting away  the  foul  matter,  would  relieve  the  air  of  the 
apartments  of  its  noxious  effluvia. 

In  order  to  prevent  the  entrance  of  any  unpleasant 
smell  through  the  apertures  by  which  the  water  goes  down, 
there  should  be  a  hell  stench-trap  at  the  commencement 
of  the  drain.  This  addition,  which  will  be  furnished  to 
order  by  the  plumber  who  constructs  the  sink,  has  the  ad- 
ditional advantage  of  retaining  particles 
of  solid  matters  that  may  fall  down.  It 
is  shown  by  figures  18,  19,  for  which  we 
are  indebted  to  Webster  s  Eneyelopcedia. 
"Fig.  18,  a  h  c  represents  the  section 
of  a  portion  of  a  hollow  cone  of  metal, 
having  a  short  pipe  in  the  middle,  h  d; 
and  water  is  put  into  this  cone  up  to  the 
level  a  e.  A  loose  perforated  cover  e  is 
made  to  rest  on  a  shoulder  on  the  top  of  the 
cone,  and  this  cover  is  perforated  with  two 
circles  of  holes;  on  the  lower  side  of  this 
cover  a  hemispherical  cup  is  fixed,  the  edges 
of  which  dip  under  the  surface  of  the  water. 
When  water  of  any  kind  is  thrown  on  the 
down  through  the  holes,  and  finds  its  way 
under  the  edges  of  the  inverted  cup,  down 
through  the  tube  d,  and  so  into  the  drain ; 
but  if  any  foul  air  should  come  back  the 
same  way,  before  it  gets  out  it  would  have 
to  pass  through  the  water;  but  from  its 
levity  it  lodges  in  the  top  of  the  hemi- 


Fig.  18. 


cover,  it  passes 

Fig.  19. 


48 


THE  LABORATORY — DRAINING  RACKS. 


spherical  cup,  and  cannot  descend  through  the  water,  unless 
more  pressure  is  exerted  than  is  usually  the  case;  hence  the 
cup  dipping  into  the  water  is  a  complete  trap  or  stop  for 
the  air,  and  effectually  hinders  any  bad  smell  or  noxious 
effluvia  from  coming  up  from  drains,  which,  indeed,  should 
never  be  without  this  simple  but  useful  contrivance.  These 
traps  likewise  prevent  the  intrusion  of  rats,  &c.  This  appa- 
ratus, however,  is  sometimes  liable  to  be  deranged  by  neglect 
or  bad  usage ;  and  it  is  proper  to  construct  another  kind,  of 
brickwork.  Somewhere  in  the  course  of  the  drain  let  there 
be  sunk  a  small  square  well,  Fig.  19,  g  g,  built  round  with 
bricks  laid  in  cement,  and  plastered  on  the  inside  with  the 
same,  so  as  to  be  completely  water-tight  and  to  remain  always 
filled  with  water.  Across  this  well  let  there  be  a  piece  of 
paving  stone  so  fixed  that  its  top  may  touch  the  cover  of  the 
drain,  and  its  lower  edge  dip  below  the  surface  of  the  water 
in  this  trap  or  well.  On  the  same  principle  as  the  bell  trap, 
no  air  can  pass  along  the  drain,  it  being  stopped  by  the  water 
below  the  stone." 

As  all  the  cleansing  operations  are  performed  at  the  sink, 
it  is  necessary  that  it  should  be  fitted  with  several  shelves,  in 
addition  to  those  which  may  be  arranged  by  its  sides.  To 
afford  free  egress  to  the  draining  water,  those  which  are  to 
hold  the  glass-ware  had  better  be  cullendered,  and  upon  one,  for 
the  safety  of  the  test  tubes  and  other  hollow  apparatus  of  too 


Fig.  20. 


Fig.  21. 


small  circumference  to  stand  upright  alone, 
there  should  be  a  series  of  draining-pins  as 
shown  by  Fig.  20.  A  rack  of  horizontal  pegs, 
for  draining  retorts  and  other  irregular-shaped 
apparatus,  might  also  be  conveniently  arranged 
upon  a  part  of  the  space.  For  draining  vials 
and  small  flasks,  an  upright  stand  fitted  with 
pegs,  as  shown  by  Fig.  21,  is  perhaps  prefer- 
able to  the  horizontal  rack. 


THE  LABORATORY — CLEANSING  APPARATUS.       49 

A  jar  of  soft  and  a  piece  of  castile  soap  should  have 
appropriate  positions  in  the  vicinity  of  the  sink ;  and  near  by 
also,  say  on  the  back  of  the  door,  for  the  sake  of  economizing 
room,  there  must  be  two  long  towels  hung  on  rollers  as  at 
Fig.  22.     One  of  these  towels  is  exclu- 
sively for  the  hands,  the  other  for  drying  Fig.  22. 
the  cleansed  glass-ware,  &c.     The  other 
accompaniments  to  the  sink  are  a  coarse 
towel,  a  small  paint-brush,  a  bottle  of 
shot,  a  series  of  wires,  some  tow  and 
raw  cotton,  and  a  wire  instrument  for 
the  removal  of  corks  from  the  interior 
of  bottles.     This  latter  is  nothing  more 
than  three  plies  of  stiff  wire  united  together  at  their  upper 
ends,  and  bent  in  angular  forms  at  their  lower  ends.     The 
paint-brush  is  for  washing  out  wide-mouthed  apparatus,  and 
can  be  well  substituted  by  a  twine-brush  of  similar  shape,  and 
much  used  in  housewifery  for  washing  tea-china.     These  and 
the  cork  wires  are  to  be  had  at  any  house-furnishing  esta- 
blishment. 

Of  the  series  of  wires,  one  should  be  stiff  and  skewer-like, 
with  pointed  end,  to  remove  those  particles  of  dirt,  tena- 
ciously adhering  to  bottles,  which  have  resisted  the  cleansing 
action  of  agitation  with  shot.  The  remaining  wires  may  be 
of  stiff  iron  and  roughened,  or  jagged  at  the  ends,  in  order 
the  more  securely  to  prevent  the  slipping  of  the  tow  or  cotton, 
which  is  wrapped  and  tied  thereon  to  facilitate  the  cleansing 
of  the  glasses.  The  tow  or  cotton  is  to  be  renewed  as  fre- 
quently as  is  necessary  to  cleanliness.  A  portion  of  the  wires 
may  be  from  J  to  J  of  an  inch  thick,  and  16  to  18  inches 
long.  The  rest  for  smaller  apparatus  may  be  of  proportion- 
ally less  dimensions.  Several  long  wedge-shaped  oaken  sticks 
are  also  convenient  for  more  effectually  applying  the  cloth  or 
towel,  with  which  they  are  temporarily  wrapped,  to  the  angular 
spaces  at  the  bottom  of  the  glasses.  All  of  these  pieces  of 
apparatus  should  have  appropriate  places  near  to  the  sink.  A 
series  of  pegs  or  nails  are  very  convenient  hangers,  and 
two  or  four  cuddies  make  serviceable  receptacles  for  the  tow, 
cotton,  and  rags. 

In  those  situations  where  it  is  not  convenient  to  introduce 
the  water  through  a  pipe,  there  must  be  erected  immediately 
over  the  sink  a  strongly  braced  shelf,  as  a  support  to  a  closely 


50 


THE  LABORATORY — THE  TOOL-CHEST. 


covered  deal  wood  cistern  for  the  reception  of  water.  The 
water  is  supplied  either  by  buckets  full  from  a  neighboring 
pump  or  else  is  pumped  in.  In  the  former  case,  the  position 
of  the  sink  in  the  corner,  and  near  to  the  door,  allows  great 
facility  in  filling  it. 

Next  to  the  sink,  occupying  the  inner  wall  spaces  on  either 
side  of  the  door,  as  at  m  m,  PI.  2,  are  strong  shelving  cuddies, 
racks,  and  pegs,  as  receptacles  for  crucibles,  furnaces,  iron 
pots,  pans,  lead  coils,  and  other  apparatus  needful  in  the 
processes  and  operations  performed  in  the  room. 

The  corner  shelves  K,  PI.  2,  strongly  built,  are  for  the  re- 
ception of  the  larger  pieces  of  apparatus.  There  should  also 
be  reserved  a  wall  space  for  the  still,  generator,  &c.,  when  out 
of  use. 

The  anvil  occupying  the  position  L,  plate  2,  and  resting 
upon  a  foot-block,  is  a  most  useful  implement,  and  a  necessary 
accompaniment  to  the  tool-chest,  upon  the  opposite  side  of  the 
room,  at  n,  PI.  2.  This  tool-chest,  which  is  shown  by  Fig. 
23,  combines  in  its  construction  the  conveniences  of  a  work- 
bench. The  vice  is  afiixed 
Fig-  23.  towards  the  end,  so  as  to 

give  full  working  room.  The 
drawers  are  receptacles  for 
the  requisite  tools,  among 
which  should  be  a  hammer, 
hatchet,  saw,  a  chisel  of 
each  kind,  gimblets,  awls, 
files  of  the  various  shapes, 
pincers,  a  soldering  iron,  a  screw-driver,  with  an  assortment 
of  screws,  nails,  &c.  A  glue-pot  will  also  be  found  a  necessary 
addendum.  The  bench  should  be  about  four  feet  in  length, 
and  of  height  suitable  to  the  comfort  and  convenience  of  the 
operator. 

The  pedestal  o,  PI.  2,  occupying  the  space  between  the 
door  and  left  front  window,  supports  a  barrel-shaped  reservoir 
of  deal  wood,  or  preferably  of  blue  stone,  (which  can  now  be 
had  at  Maulden  Perine's  pottery,  Baltimore,)  for  the  reception 
of  distilled  water,  a  supply  of  which  should  be  constantly  kept 
on  hand. 

A  tin  match-box,  an  essential  requisite  of  the  furnace  room, 
should  have  a  dry  position  in  some  convenient  place  upon  the 
wall. 


THE  LABORATORY — THE  OPERATING  ROOM. 


51 


The  charcoal,  coke,  and  sand  can  either  be  kept  in  the  cel- 
lar, or  else  in  bins  occupying  the  base  of  the  shelving,  and 
resting  immediately  upon  the  floor. 

A  solid  oaken  pedestal  for  the  iron  mortar,  and  several 
wooden  buckets  for  general  convenience,  are  also  necessary 
pieces  of  furniture. 

All  operations  emitting  corrosive  or  disagreeable  vapors 
should  be  confined,  as  far  as  possible,  to  this  room.  In  passing 
sulphuretted  hydrogen,  chlorine,  or  sulphurous  acid  through 
liquids,  the  vessels  should  rest  either  upon  a  shelf  projecting 
out  of  the  window,  or  else  under  a  hood  which  can  carry  the 
emanations  into  the  flues,  and  thus  prevent  much  corrosion 
of  apparatus  and  discomfort  to  the  operator. 


CHAPTER  IV. 


THE   OPERATING  ROOM. 


Fig.  24. 


Between  the  office  and  the  furnace  room,  and  occupying  the 
whole  residual  floor  space  C,  PL  2,  of  the  apartment,  is  the  main 
operating  room  (PI.  1 ),  of  dimensions  on  the  plan,  24  by  18.6  feet. 
In  this  room  are  performed  all  the  more  delicate  manipulations 
of  analysis  and  experimental  research,  and  hence  the  necessity 
of  great  cleanliness.  The  arrangement  prescribed  frees  it 
entirely  from  the  dust  of  the 
coarser  operations  of  the  fur- 
nace-room, (the  door  of  which 
should  be  kept  constantly 
closed,)  while  the  counter- 
poised windows,  of  adequate 
dimensions  to  afford  abundant 
light,  are  also  capable  of  main- 
taining thorough  ventilation. 
In  this  room  are  stored  nearly 
all  the  finer  apparatus  and 
materials.  The  main  feature 
of  the  apartment  is  the  ope- 
rating table,  which  is  shown 
by  Fig.  24.    Its  position  (M, 


° 

= 

o 

'Y^ 

» 

o 

o 

^ 

f 

~\ 

• 

^i 

.  »-  1 

^ 

\ 

o              1 

52  THE  LABORATORY — THE  OPERATING  TABLE. 

PI.  2)  is  against  the  front  wall  space  between  the  middle 
and  left  window.  It  may  be  constructed  of  pine  wood,  though 
cherry  or  walnut  is  preferable.  At  all  events,  the  top,  which 
must  project  over  all  around  2  inches,  should  be  either  of 
these  woods  or  ash,  and  at  least  of  an  inch  thickness;  glued  at 
the  grooves,  and  grooved  and  clamped  at  the  cross-grained  end, 
so  as  to  prevent  warping  or  shrinking,  either  of  which  creates 
a  great  inconvenience  to  the  operator.  It  is  indispensable  that 
the  stuff  be  well  seasoned  and  joined,  because  any  shrinking 
will  leave  loop  holes  for  leakings  to  penetrate  into  the  drawers 
beneath,  and  injure  their  contents.  When  the  top  is  made 
and  jointed  as  thus  directed,  it  obviates  the  necessity  of  cover- 
ing with  sheet  lead,  which,  though  more  durable,  endangers 
the  safety  of  glass  and  other  fragile  vessels  placed  upon  it. 
The  height  of  the  table  proper  is  3  feet.  Depth  2  feet  10 
inches.  The  length  of  the  top  is  4  feet  10  inches.  The  shelf- 
stand  or  test  case,  which  slides  in  grooves,  and  is  fastened  to 
the  top  of  the  table  by  screws,  is  30  inches  in  length,  and  30 
to  32  in  height.  The  distance  between  the  shelving  is  unequal, 
in  order  to  accommodate  the  different  sized  bottles.  The  space 
between  the  lower  and  first  shelf  may  be  10  inches,  diminish- 
ing gradually  upward,  so  that  the  interstice  between  the  top 
and  topmost  shelf  shall  not  be  greater  than  5  inches.  The 
shelves  may  be  of  light  stuff,  say  j  inch  thickness.  The  upper 
drawers  should  have  a  depth  of  2 J  inches  ;  the  lower  3J  inches. 
The  closets  below  should  be  fitted,  the  one  on  the  right,  with 
movable  shelves,  the  other  on  the  left  with  rows  of  wooden 
pegs,  obliquely  hung. 

This  table  thus  constructed  is  the  operating  table  of  the 
experimenter,  and  must  be  furnished  with  such  apparatus  and 
materials  as  are  in  constant  requisition,  and  hence  the  con- 
venience of  the  shelving,  drawers  and  pegs,  as  their  recepta- 
cles. As  it  is  desirable  that  the  table  should  not  be  encum- 
bered with  apparatus  in  unnecessary  amount,  only  those 
pieces  which  are  of  constant  use,  and  required  to  be  at  hand, 
should  find  an  abode  within  the  limits  of  this  table.  The 
general  supplies  of  the  laboratory  are  stored  elsewhere,  as  will 
be  directed  hereafter. 

One  of  the  upper  drawers  should  be  reserved  for  filters  of 
the  different  kinds  of  paper  used  for  the  purpose.  These  may 
be  purchased,  already  cut,  and  of  the  different  sizes,  neatly 
put  up  in  boxes,  of  Kent  of  New  York.     If  they  are  made  in 


THE  LABORATORY — THE  OPERATING  TABLE. 


53 


the  laboratory,  it  is  necessary  to  have  a  series  of  circular  tins, 
corresponding  with  the  size  of  the  funnels  most  in  use,  by 
which  to  shape  them. 

Another  drawer  may  be  reserved  for  small  tubes,  rods, 
pipettes,  and  glass  or  porcelain  connections.  Another  for 
platinum  crucibles,  spatulas  and  fine  metallic  vessels. 

The  small  retorts,  bulbs  and  the  like  should  also  have  an 
appropriate  drawer.  The  larger  retorts  and  glass  apparatus 
find  appropriate  places  in  the  cupboards. 

The  top  drawer  to  the  extreme  right  should  be  fitted  up  in 
desk-form,  and  furnished  with  pen,  ink  and  paper,  for  the  con- 
venience of  making  rough  notes  during  operations,  which  are 
afterwards  to  be  neatly  transcribed  in  a  note-book,  or  "  Record 
of  Laboratory  Operations,"  kept  especially  for  the  purpose  in 
an  appropriate  place  in  the  office  desk.  The  valuable  infor- 
mation which  can  in  this  way  be  stored  up,  in  a  short  time 
amounts  to  a  vast  fund,  which  may,  to  the  great  convenience 
and  advantage  of  the  writer,  serve  as  a  remembrancer  of  facts 
acquired  and  of  errors  avoided.  A  coarse  towel  should  always 
be  an  accompaniment  to  this  table,  and  have  a  hanging  posi- 
tion at  its  side. 

The  two  lower  drawers  beneath  the  closets  may  be  reserved 
for  the  more  weighty  implements. 

A  leaden  funnel,  supported  by  a  wooden  casing,  with  its 
barrel  united  to  a  leaden  pipe  leading  through  the  floor  into 
the  street  gutter,  and  placed  immediately  to  the  right  of  the 
table,  would  be  very  convenient  for  receiving  and  conveying 
off  the  slops  from  the  test  tubes.  When  this  arrangement  is 
not  practicable,  a  bucket  must  be  substituted,  and  emptied 
daily,  for  the  practice  of  emptying  test  tubes  upon  the  floor  is 

Fig.  25. 

JJJJJJUUJJJL 


mMmMif 


54 


THE  LABORATORY — THE  SPIRIT  LAMP. 


Fig.  26. 


slovenly  and  reprehensible,  and  by  keeping  it  constantly  damp, 
the  comfort  of  the  operator  is  greatly  impaired. 

A  rack  with  test  tubes,  Fig.  25,  may  be  considered  one  of 
the  fixtures  of  the  operating  table. 

The  spirit  lamp  which  furnishes  the  heat  for  table  opera- 
tions, and  is  shown  by  Fig.  26,  will  be  spoken  of  more 
fully  hereafter.  When  coal  gas  can 
be  commanded,  it  is  far  more  con- 
venient and  economical,  and  by  a 
particular  arrangement,  may  be  made 
to  yield  heat  enough  for  evaporation 
and  ebullition  in  capsules,  and  the 
different  operations  of  digesting  in 
bell  glasses,  &c.  By  the  use  of  a 
large  argand  burner  fixed  over  the 
jet  of  the  table  blow-pipe.  Fig.  30 
we  can  obtain  the  power  of  a  blast. 
The  admixture  of  the  gas,  in  this  way, 
with  atmospheric  air,  increases  the 
heat  to  such  an  extent  as  to  allow 
the  ignition  of  precipitates  in  cruci- 
bles, and  the  almost  entire  dispensa- 
tion of  FURNACE  fires  in  table  opera- 
tions. The  arrangement  by  which 
these  results  are  accomplished,  so  as 
to  avoid  entirely  the  deposition  of 
carbon  on  the  bottoms  of  the  vessels,  is  shown  by  Fig.  27.    B 

is  a  cylinder  of  sheet  cop- 


Fig.  27. 


lead  depending  from. 


per,  stretched  over  the  top 
of  which,  and  fastened  by 
an  iron  hoop,  is  a  fine  wire 
gauze,  covered  with  fine 
gravel  to  protect  it  from 
wear  and  tear.  In  order 
to  promote  a  more  tho- 
rough admixture  of  the 
gas  and  atmospheric  air, 
(which  is  effected  in  the 
chimney,)  there  is  a  coarse 
wire  gauze  diaphragm  c. 
The  gas  pipe  of  flexible 
and   connected  by  a  gallows   screw 


THE  LABORATORY — THE  GAS  FURNACE.  55 

A,  with  the  permanent  hanger  o,  terminates  in  an  argand 
burner  d.  To  prevent  a  scorching  of  the  table,  the  burner 
and  cylinder  both  rest  upon  a  fluted  plaster  tile.  The  air 
enters  through  the  openings  in  the  lower  circumference,  being 
drawn  up  by  the  upward  current  of  gas,  which  is  let  on  and 
regulated  by  the  stop-cock  r;  and  the  mixture  thus  formed 
passing  through  the  upper  fine  wire  gauze,  above  which  it  is 
ignited,  should  burn  with  a  bluish  flame. 

"  Where  the  quantity  of  gas  is  too  great  for  the  amount  of 
air  admitted,  the  flame  will  be  white  and  smoky,  but  by  regu- 
lating the  supply  of  gas,  the  due  proportion  for  a  blue  flame 
may  be  easily  attained.  Now,  to  obtain  a  blue  flame  from  a 
cylinder  of  large  diameter,  a  considerable  quantity  of  gas  will 
be  requisite,  and  hence  an  economical  advantage  is  gained  by 
employing  cylinders  of  different  diameters.  In  the  same 
cylinder,  also,  where  different  quantities  of  heat  are  desired, 
the  lower  series  of  holes  may  be  made  large,  and  a  ring  of 
sheet-iron  slid  over  them,  by  which  the  quantity  of  air  ad- 
mitted may  be  regulated  according  to  the  quantity  of  gas 
consumed.  The  cylinders  may  be  2  J  to  5  inches  diameter  by 
6 — 8  inches  in  height ;  but  by  introducing  several  pieces  of 
coarse  gauze,  <?,  at  short  distances  apart,  the  height  may  be 
diminished.  The  highest  amount  of  heat  produced  by  this 
apparatus  is  a  cherry-red  by  daylight.  For  burning  off"  filters 
in  a  platinum  crucible,  a  cylinder  of  2J  inches  diameter  is 
amply  sufficient ;  but  for  heating  larger  vessels,  such  as  cap- 
sules, those  of  4 — 5  inches  diameter  are  desirable.  This  mode 
of  burning  the  gas  presents  the  advantages  of  producing  any 
degree  of  heat  as  high  as  a  red,  of  not  blackening  vessels  im- 
mersed in  the  flame,  and  of  avoiding,  with  more  certainty,  the 
fracture  of  porcelain  or  glass  vessels,  from  the  diffusive  cha- 
racter of  the  flame." 

The  ring  n,  sliding  upon  the  rod  of  the  upright  stand  A, 
serves  as  a  support  for  a  retort,  capsule  or  crucible.  A  second 
chimney  g  placed  over  the  crucible  creates  a  uniform  and 
constant  draught. 

The  whole  of  this  apparatus  is  movable,  and  when  the  space 
which  it  occupies  upon  the  table  is  required  for  other  purposes, 
it  is  only  necessary  to  disconnect  it  from  the  hanger,  and 
place  the  whole  aside,  to  be  as  readily  replaced  again  when 
wanted. 

The  introduction  of  gas  into  the  room  also  allows  the  substi- 


56 


TH5  LABORATORY — THE  TABLE  SAND-BATH. 


tution  of  an  economical  table  sand-bath  (Fig.  28),  for  the  more 
cumbersome  one  described  at  pp.  30,  31.    It  consists  of  a  copper 

Fig.  28. 


Y 


box  B  eighteen  inches  long,  twelve  inches  wide  and  six  inches 
deep.  The  top,  which  is  lodged,  projects  over  about  an  inch 
and  forms  the  bed  for  the  sand.  The  door  c  having  a  small  semi- 
circular opening  at  its  base,  is  for  the  entrance  of  the  gas 
pipe  with  an  argand  burner  attached,  as  well  also  for  the 
supply  of  air  necessary  to  sustain  combustion.  The  fire  thus 
applied  heats  the  sand  on  the  top.  The  heated  air  has  an 
exit  through  the  circular  aperture  a,  after  having  traversed 
the  interior,  which  is  divided  lengthwise  by  the  partition 
as  represented  by  the  dotted  lines.  The  communication 
between  the  apartments  is  by  an  opening  d  in  the  dia- 
phragm. In  this  way  we  obtain  a  graduation  of  the  tem- 
perature of  the  bath.  The  Swedish  chemists  improve  upon 
this  construction,  by  annexing  an  apartment  for  drying  filters 
and  precipitates  as  well  as  for  keeping  liquids  hot  while  filter- 
ing. 

These,  with  the  test  bottles  and  contents,  complete  the  para- 
phernalia of  the  operating  table,  and  so  we  proceed  to  describe 
the  next  most  important  piece  of  furniture  of  the  room. 

The  Centre  or  G-eneral  Table. — This  table,  (N,  PI.  2,)  com- 
pactly fitted  to  serve  the  double  purpose  of  an  operating  table 
for  distillations,  and  other  large  general  operations  of  the  labo- 
ratory which  would  occupy  too  much  room  upon  the  smaller 
table.  Fig.  24,  has  its  top,  also  of  cherry,  projecting  two 
inches  all  around  and  grooved,  glued  and  tightly  jointed,  as 
directed  for  the  preceding  table,  like  which,  its  lower  portions 
may  also  be  of  white  pine.     Its  position  is  near  the  centre  of 


THE  LABORATORY — THE  CENTRE-TABLE.        57 

the  room,  so  as  to  afford  free  access  to  all  its  sides.     Fig.  29 

Fig.  29. 


!    Hi  -    !l    -  li    »  1!    HI   ^  II    -   1 

1         O                     O                   O           j          o 

i- 

u                \ 

Id 

i 

gives  a  view  of  it.  Its  dimensions  are  2.10  feet  height; 
%,^  feet  length;  and  3.4  inches  breadth.  In  order  to  ensure 
perfect  stability,  the  legs  are  fitted  to  a  bed  which  is  to  be 
firmly  screwed  to  the  floor,  so  that  the  table  may  be  stationary 
and  free  from  oscillatory  motion,  as  any  jarring  may  create 
serious  damage  to  a  delicately  arranged  apparatus. 

The  drawer  space  should  not  exceed  15  inches  of  the  whole 
height  of  the  table.  The  end  drawers  are  necessarily,  from 
the  construction  of  the  table,  very  short,  and  may  be  omitted 
entirely,  though  it  is  better  policy  to  have  as  many  receptacles 
as  possible,  for  they  will  all  be  found  useful  as  well  as  con- 
venient. 

Of  the  front  drawers,  one  should  be  appropriated  exclu- 
sively to  the  sheets  and  other  articles  of  India  rubber.  Ac- 
companying these  must  also  be  a  pair  of  shears  and  a  ball  of 
very  fine  linen  twine  for  fashioning  and  securing  joints. 
Another  drawer  must  be  reserved  exclusively  for  the  corks  of 
assorted  sizes.  Two  smaller  apartments  or  divisions  are  also 
necessary,  one  for  the  rat-tail  files  of  different  sizes,  and  the 
other  for  the  cork  borer,  of  which  more  will  be  said  hereafter. 

The  stock  of  filtering  paper  is  also  kept  in  another  of  these 
drawers;  and  with  it,  the  circular  tins  by  which  it  is  cut 
into  different  sized  filters.  The  shears  for  cutting  the  paper 
should  be  kept  always  sharp  and  clean.  Another  drawer 
divided  into  compartments  is  required  for  the  reception  of  tow, 
5 


58 


THE  LABORATORY — THE  BLOW-PIPE. 


raw-cotton,  bladders,  string,  &c.;  and  another  for  the  clean 
dusters  and  towels  of  the  establishment. 

The  filtering  cloths  and  material  for  that  purpose  are  also 
kept  in  a  separate  drawer.  The  thermometers  and  hydro- 
meters are  likewise  kept  in  a  distinct  drawer. 

There  are  many  other  articles  which  are  better  preserved 
in  drawers,  and  hence  there  is  a  necessity  for  the  whole  num- 
ber in  the  table.  The  short  drawers  in  the  end  of  the  table 
can  be  reserved  for  minor  matters,  such  as  the  scratching- 
diamond  and  similar  implements. 

The  lower  bed  of  the  table  forms  an  excellent  shelf  for  the 
filter  stands,  retort-holders,  clamps,  supports,  and  other  wooden 
apparatus  in  frequent  use  upon  the  operating  table. 

All  the  iron  stands  and  similar  apparatus  should  be  painted 
with  black  varnish*  in  order  to  preserve  them  from  rust.  In 
the  selection  of  iron  hollow-ware  for  purposes  of  ebullition, 
or  evaporation,  choose  that  which  is  enameled  internally ; — it 
is  more  convenient,  readily  cleansed,  and  not  much  more  costly 
than  the  naked  iron  ware. 

The  mouth  blow-pipe  table  occupying  a  position  against 
the  front  wall,  and  immediately  under  the  right  window,  as 

Fig.  30. 


*  To  fused  asphaltum,  40  ozs.,  add  a  half  gallon  of  boiled  linseed  oil,  6  ozs. 
each  of  red  lead  and  litharge,  4  ozs.  dried  and  powdered  white  copperas.  Boil 
for  two  hours,  then  mix  in  8  ozs.  of  fused  dark  amber  gum,  and  a  pint  of  hot 
linseed  oil,  and  boil  again  for  two  hours  more.  When  the  mass  has  thickened, 
withdraw  the  heat  and  thin  down  with  a  gallon  of  turpentine. 


THE  LABORATORY — THE  AIR-PUMP.  59 

shown  at  p  PI.  2,  is  an  indispensable  piece   of  apparatus 
which  will  be  more  fully  spoken  of  under  blow-pipe  operations. 

The  blast  or  pneumatic  table  (shown  in  position  at  q  PI. 
2),  which  is  sometimes  also  called  the  table  blow-pipe,  may  be 
considered  as  an  implement  indispensable  to  the  chemist,  it 
being  alike  useful  for  bending  glass  tube,  blowing  bulbs  and 
other  small  apparatus,  and  for  rapidly  effecting  the  decompo- 
sition and  ignition  of  substances,  which,  for  their  fusion,  would 
require  an  ordinary  wind  furnace.  The  most  convenient  form 
of  this  apparatus  is  shown  by  Fig.  30.  The  drawing  is  taken 
from  one,  in  Professor  Booth's  laboratory,  made  by  J.  Bishop, 
machinist  of  this  city.  It  consists  of  a  brass  cylinder  piston 
2,  worked  by  a  treadle  which  drives  the  air  into  a  large  tin 
box  enclosed  in  a  frame-work  1  immediately  under  the  top 
of  the  table.  From  the  front  end  of  the  box  a  tube  rises 
through  the  table  top,  and  terminating  with  its  small  jet 
within  the  interior  of  an  Argand  burner,  urges  the  air  di- 
rectly upwards,  producing  a  full  flame.  The  Argand  burner 
may  be  connected  with  a  lamp  or  reservoir,  containing  a  solu- 
tion of  oil  of  turpentine,  or  alcohol,  or  with  a 
gas  pipe.  In  the  former  case,  the  burner  has  Fig-  3i. 
a  circular  wick  with  a  contrivance  for  adjust- 
ing its  height.  The  latter,  being  neater,  and 
always  ready,  is  almost  exclusively  used  in  the 
laboratory,  as  giving  a  powerful  flame  which  may 
be  elevated  or  depressed  at  pleasure.  With  one  of 
the  new  fashioned  Argand  gas  burners  as  shown  by  Fig.  31, 
this  table  forms  an  excellent  substitute  for  ordinary  furnace 
operations. — (Encyelopoedia  of  Chemistry.) 

Air-Pump, — The  small  table,  at  r  PI.  2,  is  used  for  the 
air-pump  which,  when  not  in  use,  should  be  kept  in  an  appro- 
priate place  in  one  of  the  cases  in  the  balance  room.  Being 
a  costly  apparatus,  it  is  now  almost  exclusively  replaced 
by  syringes,  which  are  more  economical  and  not  much  less 
convenient,  as  made  for  the  purpose  at  the  present  time. 
For  the  sake  of  a  convenient  uniformity,  the  attachment 
screws  should  have  a  thread  similar  to  that  of  the  stop- 
cock, so  as  to  admit  of  a  ready  adaptation  to  each  other 
when  an  attachment  is  to  be  effected.  Of  the  many  opera- 
tions in  which  the  syringe  is  made  to  assist,  may  be  men- 
tioned the  displacement  of  air  in  retorts,  globes,  and  other 
vessels,  &c.,  previous  to  the  introduction  of  gases,  and  also  in 


60 


THE  LABORATORY — THE  AIR-PUMP. 


the  exhaustion  of  receivers  for  experiments  with  atmospheres 
of  less  than  ordinary  pressures. 

In  order  that  these  machines  may  work  properly,  it  is  ne- 
cessary that  the  joints  should  be  tight  and  free  from  leakage, 
and  that  the  pistons  be  well  oiled  so  as  to  promote  their  easy 
motion.  An  excellent  method  of  preserving  this  apparatus 
in  good  order,  is  to  work  it  frequently  even  when  not  in  use, 
for  by  this  mode,  the  elasticity  of  the  pistons  and  ready  play 
of  the  cocks  may  be  retained.    Fig.  32  represents  a  horizontal 

«r  Fig.  32. 


double  cylinder  air-pump,  invented  by  A.  L.  Kennedy,  M.  D., 
of  this  city.  The  advantages  of  this  apparatus  over  the  old 
form,  are  stability  and  portability,  and  greater  cheapness. 
Besides,  it  is  more  easily  and  readily  worked.  Unlike  the 
upright  cylinders,  this  pump  is  not  liable  to  tilt  over  whilst 
being  worked,  and  consequently  there  is  not  that  instability 
so  annoying  when  using  the  barometer  gauge. 

"In  the  figure,  L,  L  represent  the  barrels,  the  enlarged  ends 
of  which  are  let  into  the  board  and  bolted  through  to  insure 
stability.  There  is  one  rack;  the  two  pistons  being  attached 
to  its  extremities.  A  portion  of  the  rack  is  exposed  at  T. 
The  semi  pinion  w,  works  in  cast  straps,  or  gudgeons,  attached 
to  the  bottom  of  the  board  by  screws,  which,  passing  through, 
terminate  in  the  rack  guides,  one  of  which  is  seen  above. 
The  forward  gudgeon  is  so  cast  as  to  receive  the  end  of  the 
clamp  which  secures  the  pump  to  the  table.     The  semi-pinion 


THE  LABORATORY — THE  AIR-PUMP.  61 

works  upwards  through  a  slot  cut  in  the  board,  and  of  course 
between  the  rack  guides.  The  upper  extremities  of  the  guides 
are  perforated  to  receive  rollers,  against  which  the  back  of 
the  rack  may  work  when  necessary.  None  have  yet  been 
required.  To  the  axis  of  the  semi-pinion  the  handle  is  attached 
in  the  usual  manner.  The  piston  may  be  either  solid  or 
valved,  and  the  cylinders  may  communicate  with  the  plates 
R  and  B,  in  the  way  most  approved  by  the  maker.  In  the 
pump  from  which  the  sketch  is  taken,  the  pistons  are  solid. 
The  farther  extremities  of  the  cylinders  bear  female  screws, 
which  connect  with  corresponding  male  screws  on  the  block. 
On  the  posterior  portion  of  each  block  is  cut  a  female  screw; 
the  male  of  which  bears  the  valve,  of  course  opening  inwards, 
V,  V.  On  those  portions  of  the  blocks  which  project  into  the 
board  are  cut  male  screws  bearing  valves  opening  outwards. 
Perforated  nuts  over  these  secure  the  blocks  to  the  board,  and 
the  valves  against  injury.  At  v,  v  is  attached  the  tube  lead- 
ing from  the  plates.  D  is  the  screw  for  restoring  atmospheric 
pressure.  The  general  stop-cock  s,  connects  this  with  the 
parallel  tube  which,  bearing  the  gauge  cock  s',  forms  at  plea- 
sure a  communication  between  the  plates. 

The  original  of  the  figure  both  exhausts  and  condenses. 
The  remaining  letters  refer  to  the  parts  used  in  condensing. 
This  is  effected  by  simply  connecting,  by  means  of  tubes  under 
the  board,  the  valves  f',  f  with  a  third  tube  passing  upward 
to  the  stop-cock  K.  Then  the  air  drawn  in  at  R,  will  be  con- 
densed in  a  receiver  screwed  on  c.  Those  familiar  with 
Pneumatic  chemistry  need  not  be  told  of  the  facilities  thus 
afforded  for  the  transfer  of  gases.  The  condensing  gauge  is 
borne  by  the  screw  G.  To  the  practical  chemist,  it  is  un- 
necessary to  dilate  upon  the  advantages  that  result  from  lower- 
ing the  centre  of  motion  to  a  level  with  the  points  of  support, 
bringing  both  plates  directly  under  the  operator's  eye,  and 
presenting,  at  about  the  cost  of  an  ordinary  exhausting  pump, 
an  instrument  furnished  with  all  the  facilities  for  exhaustion, 
transfer  and  condensation,  without  any  shifting  of  parts." 

The  table  s  PI.  2,  to  the  right  of  the  air-pump,  is  a  stand 
for  the  common  scales  of  the  laboratory,  which  are  useful  for 
testing  the  weights  of  materials  purchased  and  for  weighing 
coarser  articles  in  large  quantities.  A  cheap  platform  balance 
with  a  movable  tin  dish  answers  conveniently  for  this  purpose. 
The  accompanying  (Avoirdupois)  set  of  weights  should  range 
from  \  oz.  to  8  lbs. 


62  THE  LABORATORY — THE  CUPBOARDS. 

The  next  fixtures  to  be  described  are  the  cupboards.  Those 
affixed  to  the  partition  of  the  furnace  room  as  at  t  and  u  PI. 
2  are  more  properly  shelves,  with  curtains  instead  of  doors  to 
protect  their  contents  from  the  dust.  The  set  t  may  be  occu- 
pied with  the  leaden  coils,  wooden  and  coarser  apparatus  of 
the  apartment.  The  curtains  of  common  muslin,  rendered 
fire  proof  by  immersion  in  a  solution  of  borax  and  sal  ammo- 
niac and  drying,  are  hung  by  means  of  small  brass  rings  upon 
an  iron  rod  running  the  whole  length  of  the  cap  of  the  shelv- 
ing; and  in  order  to  keep  them  distended,  leaden  bullets 
should  be  sewed  at  occasional  distances  upon  the  lower  ends. 
The  shelving  u  ascends  to  only  half  the  height  of  that  of  t 
because  the  upper  space  is  to  be  reserved  for  racks  and  rings. 
The  shelves  are  intended  as  receptacles  for  the  porcelain  cap- 
sules, crucibles,  &c.,  the  bell,  beaker  and  other  similar  glass 
apparatus,  always  taking  care  to  occupy  the  lower  shelves 
with  the  larger  and  heavier  articles.  The  tube  rack  is  nothing 
more  than  a  series  of  pegs,  placed  closely  adjoining  in  a 
straight  line  and  inclining  upwards  so  as  to  prevent  the  tubes 
from  falling  through.  This  open  work  presents  the  whole 
stock  of  tubing  to  view  at  one  glance,  and  enables  a  ready 
selection  of  any  particular  piece  of  rod  or  tube.  The  smaller 
pieces  which  would  be  apt  to  fall  through,  should  be  kept  in 
a  drawer  of  the  centre  table  specially  appropriated  for  the 
purpose.  The  remaining  portion  of  the  upper  space  must  be 
furnished  with  a  series  of  various  sized  spikes  to  hold  retort 
and  flask  rings.  These  rings,  readily  made  of  wire,  vary  in 
size  from  a  half  to  two  or  more  inches  in  diameter,  and  receiv- 
ing the  necks  of  retorts  and  other  curved  or  bent  apparatus, 
retain  them  in  a  safe  and  convenient  position.  The  rings 
may  also  occupy  any  small  vacancies  upon  the  walls  for  the 
use  of  such  a  portion  of  the  apparatus  as  the  cupboard  cannot 
contain. 

The  small  cupboard  {v  PI.  2)  in  the  corner  opposite,  may 
be  used  as  a  sort  of  general  cupboard  for  very  nice  little  mat- 
ters, which  require  great  care  and  cleanliness  in  their  preser- 
vation. The  door  consequently  should  be  fitted  with  a  fastening 
and  kept  constantly  closed  when  not  in  use. 

The  cupboards  w  and  x  erected  against  the  partition 
opposite,  and  occupying  the  spaces  on  either  side  of  the 
entrance  into  the  office  are,  the  one  x  for  the  stock  of  drugs 
and  chemicals;  the  other  w  for  the  new  empty  bottles,  to  be 


THE  LABORATORY — THE  BOTTLES.  63 

confined  to  the  lower  shelves,  and  for  the  specimens  that  may 
from  time  to  time  be  accumulated  by  the  labors  of  the  opera- 
tor. The  lower  half  of  the  cupboard  X  should  be  furnished 
with  small  drawers  similar  to  a  druggist's  case.  These  are 
for  the  dye  woods,  sulphur,  chalk,  and  other  similar  coarse 
articles  of  stock  which  are  more  securely  kept  in  this  way  than 
in  bundles,  which  are  liable  to  rupture  and  damage  by  rough 
handling  and  by  retaining  moisture.  The  upper  shelv- 
ing is  to  be  exclusively  occupied  with  the  articles  in  bottles, 
which  are  to  be  arranged  in  groups,  the  compounds  of  each 
base  forming  a  group.  The  mineral  and  vegetable  acids  and 
organic  compounds,  have  also  each  a  separate  position.  The 
weightier  articles  as  elsewhere  directed,  should  always  occupy 
the  lower  shelves,  both  for  convenience  of  handling  and  on 
account  of  their  greater  stability  and  power  of  bearing  heavier 
weights  than  the  upper  shelves. 

The  black  board  y  PI.  2,  is  hung  sash-like  between  the  up- 
rights of  the  cupboard  w  and  x  and,  being  counterbalanced  by 
weights,  can  be  lowered  or  raised  at  will,  and  thus  presents 
no  hindrance  to  egress  or  ingress  from  and  to  the  office.  For 
rough  calculations  and  plans,  drafts  of  apparatus,  diagrams, 
&c.,  the  black  board  is  very  convenient.  When  a  hand  slate 
is  substituted,  the  pencil  should  be  of  talc  (French  chalk) 
which  makes  a  more  distinct  mark  than  the  common  slate 
pencil,  and  gives  more  facility  in  writing.  These  pencils 
are  now  sold  in  most  of  the  stationery  stores. 

Bottles. — Particular  regard  must  be  had  to  the  shape 
and  material  of  bottles  for  laboratory  use.  Those  intended 
for  holding  acids  or  salt  solutions,  must  be  of  well  annealed 
glass,  which  is  free  from  lead  and  can  resist  the  corrosive 
action  of  their  contents.  Some  glasses  containing  an  excess 
of  alkali,  gradually  lose  their  brilliancy  by  absorption  of  mois- 
ture from  the  atmosphere;  others  again  are  attacked  by  acid 
and  alkaline  solutions ;  and  some  indeed,  even  by  prolonged 
contact  with  boiling  water. 

The  inalterability  of  glass  by  air  or  chemical  agents  (hydro- 
fluoric acid  excepted)  is  proportional  to  its  hardness  and  infu- 
sibility.  Flint  glass  is  the  most  brilliant  and  comparatively 
fusible,  and  its  consequent  pliability  renders  it  available  for 
thermometer  and  barometer  tubes,  but  as  material  for  chemi- 
cal vessels  it  is  far  inferior  to  the  Bohemian  glass  (a  silicate 
of  potassa  and  lime  with  large  traces  of  alumina),  which  is 


64 


THE  LABORATORY — THE  BOTTLES. 


harder,  lighter,  and  while  possessing  many  better  qualities 
for  chemical  ware  is,  when  well  made,  scarcely  less  remarkable 
for  beauty  than  crystal  lead  glass. 

Care  must  be  taken  in  the  selection  of  glass  apparatus, 
especially  those  which  are  to  serve  as  implements  for  reactions, 
to  choose  such  as  are  free  as  possible  from  striae,  knots,  or 
bubbles,  defects  owing  to  the  imperfect  mixture  of  the  mate- 
rials of  the  glass.  The  more  transparent  the  glass,  the  more 
readily  can  the  interior  cleanliness  of  the  vessel  be  ascertained. 
The  common  green  glass  bottle  from  the  factories  of  New 
Jersey,  in  the  absence  of  better,  answers  every  purpose  for 
the  common  acids,  coarser  dry  substances,  and  the  solutions 
of  such  as  are  soluble;  and  are,  moreover,  economical.  For 
the  reagents  and  finer  chemicals,  there  is  a  cheap  white  glass, 
free  from  lead,  manufactured  at  Storms  and  Fox's  Fac- 
tory in  Kensington,  Philadelphia,  which  is  well  adapted  to 
the  purposes,  and  replaces  sufficiently  the  elegant,  but  at 
the  same  time  much  more  costly  Bohemian  glass  which  is 
only  to  be  obtained  by  importation.  The  laboratory  series 
should  vary  in  size  from  one  ounce  to  one  gallon,  ranging  as 
follows,  1,  2,  4,  8, 16,  32,  64, 128  ounces.  The  most  approved 
shapes  are  shown  by  the  cuts  below.     Fig.  33  represents  a 

wide  mouth  bottle  for  pow- 
ders and  crystals.  It  is 
short  and  wide,  with  round 
shoulders  to  admit  of  ready 
emptying  and  cleansing, 
and  has  a  strong  tall  neck 
for  tightly  corking.  The 
corks  should  be  perfectly 
smooth  and  of  the  velvet 
kind.  This  shape  is  equal- 
ly applicable  to  the  bottles 
of  white  glass,  as  is  also  that 
of  the  narrow  mouth,  glass 
stoppered,  as  shown  by  Fig. 
35.  The  narrow  necks  and  their  stopples,  must  be  accurately 
ground  so  as  to  insure  perfect  tightness.  As  the  cost  of  this 
white  glass  above  mentioned  is  so  very  little  greater  than  the 
Jersey  green,  it  would  probably  be  more  advisable  to  purchase 
the  whole  suite  of  bottles  of  such  material.  The  stopples  of 
the  narrow-necked  bottles  are  made   nearly  spherical,  but 


Fig.  33. 

Fig.  34. 

Fig.  35 

1 

1 

THE  LABORATORY — THE  BOTTLES.  65 

somewhat  flattened  on  the  top  to  project  over  the  mouth  so  as 
to  protect  it  from  dust.  The  lips  are  flat  and  stout  for  pour- 
ing readily.  The  wide  mouthed  stoppered  bottles  are,  as  to 
body,  similar  in  shape  to  the  above,  but  their  stopple-heads 
are  flattened  and  cover  both  the  mouth  and  the  rim.  The 
series  of  all  these  bottles  consists  of  the  sizes  above  mentioned. 
For  one  or  two  substances  both  in  solid  and  solution,  which 
are  sensitive  to  the  decomposing  influence  of  the  light,  nitrate 
of  silver  and  protochloride  of  mercury  for  instance,  it  is  ne- 
cessary that  the  bottles  be  either  of  dark  colored  glass  or  else 
covered  exteriorly  with  tin  foil.  For  hydrofluoric  acid  a  lead  bot- 
tle is  necessary,  as  glass  is  decomposed  by  that  body.  All  solu- 
tions should  be  kept  in  ground  stoppered  bottles,  and  if  economy 
is  indispensable,  let  the  series  consist  of  as  many  of  the  green 
glass  bottles  as  possible,  retaining  only  as  many  of  the  white 
Bohemian  glass  as  are  absolutely  necessary  for  the  finer  re- 
agents. Corked  bottles  are  inconvenient  and  liable  to  leakage, 
and  their  use  as  permanent  receptacles  of  liquid  should,  if 
possible,  be  entirely  discarded.  We  have  consequently  not 
given  the  shape  of  a  narrow-mouthed  unstoppered  bottle, 
though  if  they  must  be  had,  the  shape  of  Fig.  34  with  the 
neck  narrowed  must  be  the  pattern. 

All  bottles  with  contents  must  be  labeled  in  full  and  with 
symbols.  This  injunction  as  to  labeling  applies  with  equal  force 
to  the  beaker  glass  upon  the  sand-bath  and  the  capsule  over  the 
lamp,  and  to  every  vessel  resting  upon  the  shelves  or  employed 
in  operations,  which  contain  any  substance  or  solid,  whether 
the  material  or  product  of  any  process.  An  omission  of 
this  precaution  frequently  leads  to  much  confusion,  and 
occasionally  to  serious  errors.  Thin  writing  paper  glazed 
upon  one  side  wdth  a  solution  of  gum  tragacanth,  and  divided 
into  small  squares  of  difi'erent  dimensions  to  suit  the  several 
sizes  of  vessels,  answers  very  well  for  the  purpose  of  labeling 
operating  vessels.  With  a  pencil,  or  more  properly  pen  and 
ink,  the  designation  may  be  written  on  the  label,  and  thus 
completed,  is  to  be  pasted  on  the  bottle.  For  bottles  contain- 
ing the  chemicals,  materials,  &c.,  these  paper  squares  are 
equally  applicable,  but  for  the  test  series  upon  which  the  labels 
are  to  be  permanent,  it  is  better  that  the  names  be  etched 
upon  the  glass  by  the  action  of  fluohydric  acid.  In  England 
they  manufacture  a  bottle  for  this  purpose,  with  indelible 
names  in  black  enamel,  upon  a  white  ground.    They  are,  how- 


66 


THE  LABORATORY — CLEANSING  OF  GLASSWARE. 


Fig.  36. 


ever,  costly.  As  a  substitute  for  either  of  the  two  latter,  are 
printed  labels  after  the  patterns  of  those  published  by  La  Rue 
&  Co.  (110  Bunhill  row,  London),  which  contain  the  full 
name  of  the  articles,  its  symbol,  and  equivalent.  Those  bot- 
tles of  the  test  series,  which  are  to  contain  the  acids  or  other 
corrosive  liquids,  wholly  or  in  part  volatile,  should  be  provided 
with  ground  glass  caps.  Fig.  36  represents  a  bottle  of  this 
pattern  with  the  label  corroded  in  by  fluohydric  acid. 
The  mouths  of  all  the  test  bottles  should  flange  in  order 
to  facilitate  pouring.  The  last  drop  of  liquid  gene- 
rally adhering  to  the  lip  can  be  arrested  by  touching 
it  with  the  stopple,  which  catches  and  re-conveys  it 
to  the  bottle  when  returned  to  the  mouth.  Let  it 
therefore  be  a  cardinal  rule  of  the  laboratory,  that 
no  experiment  or  operation  shall  be  abandoned  even 
for  a  moment  without  having  the  receptacle  labeled. 
There  are  other  laboratory  uses,  independent  of 
the  aforementioned,  to  which  bottles  are  applicable.  The  wide- 
mouthed  when  accurately  stoppered  and  rendered  air  tight 
in  the  mouth  with  a  little  lard  or  suet,  are  excellent  substitutes 
for  jars,  for  the  reception  and  safe  keeping  of  gases  which  are 
soluble  in  water  or  corrosive  of  mercury,  and  consequently 
cannot  be  collected  over  either. 

Cleansing  of  Gflassware. — When  bottles  or  glassware  are 
greasy,  the  aid  of  alkali  or  ashes  is  necessary  for  its  removal. 
In  open  vessels  bran  or  saw-dust,  by  their  mechanical  action, 
will  cleanse  the  surface  of  grease.     In  either  case  hot  water 

is  a  great  assistant.  An  iron  or 
copper  kettle.  Fig.  37,  fitted  to  the 
top  of  the  stove  or  one  of  the  open- 
ings in  the  top  of  the  furnace,  is  a 
convenient  vessel  for  furnishing  a 
constant  supply.  The  rinsing  after- 
wards may  be  with  cold  water.  A 
short  twine  brush,  similar  to  that 
used  by  housewives  for  washing 
tea  things,  is  an  excellent  assist- 
ant in  cleansing  operations,  and 
there  should  be  several  of  them 
about  the  laboratory.  For  alkali,  lime  as  an  example,  which 
coats  the  sides,  a  little  common  muriatic  acid  is  requisite. 
When  the  dirty  matter  is  fixed  and  resists  the  purifying  action 


Fig.  37. 


THE  LABORATORY — CLEANSING  OF  GLASSWARE.     67 

of  these  two  agents,  and  also  of  hot  water,  resort  must  be  had 
to  the  use  of  shot,  which,  when  agitated  with  a  little  water 
in  the  interior  of  the  bottle,  gradually  removes  the  adherent 
dirt,  which  can  then  be  rinsed  out  with  clean  water.  Care- 
lessness in  leaving  behind  one  or  more  shot,  which  frequently 
secrete  themselves  in  the  crease  at  the  bottom,  may  result  in 
injury  to  the  next  contents  of  the  bottle,  if  it  be  solvent  of 
metal.  Coarse  sand  and  angular  pebbles,  which  are  some- 
times substituted  for  shot,  are  apt  to  scratch  the  glass,  a  dis- 
advantage which  does  not  apply  to  small  round  pebbles.  The 
daily  ablution  of  apparatus  had  better  be  performed  at  the 
close,  and  after  the  labors  of  the  day,  so  that  the  advantage 
of  the  night  may  be  obtained  for  draining  and  drying.  Re- 
torts and  beaked  vessels  should  be  ranged  on  shelves  with 
circular  holes  for  the  reception  of  their  beaks.  In  this  case  as 
well  also  in  that  of  open  vessels,  the  mouths  should  always  be 
placed  downwards.  When  it  is  necessary  to  dry  the  cleansed 
vessel  for  immediate  use,  it  may  be  well  wiped  with  a  towel 
exteriorly  and  then  placed  upon  a  moderately  heated  sand  bath, 
which  will  soon  expel  all  internal  moisture.  Wide  mouthed 
vessels  can  be  dried  with  a  cloth.  For  cleansing  test  tubes,  a 
goose-feather  or  stick  with  a  small  sponge  fastened  to  its  lower 
end  is  very  convenient. 

The  removal  of  corks  from  the  interior  of  bottles  is  eflPected 
by  an  instrument  consisting  of  four  strands  of  iron  wire,  of 
about  one  foot  length  each,  united  together  at  one  end,  and  at 
the  other  four  extremities  bent  into  an  angular  shape.  Being 
elastic,  there  is  no  impediment  to  its  passage  through  the  mouth 
of  the  bottle,  in  the  interior  of  which  it  is  made,  by  a  dexterous 
management,  to  catch  and  secure  the  cork,  which  can  then  be 
drawn  out  with  the  wire.  This  simple  little  instrument  is  to 
be  purchased  at  any  house-furnishing  bazaar.  A  very  con- 
venient substitute  is  a  doubled  string ;  the  loop  thus  formed, 
when  introduced  into  the  bottle,  secures  the  cork  and  allows 
its  easy  extraction. 

It  not  unfrequently  happens  with  ground-stoppered  bottles, 
in  cases  where  certain  substances  form  their  contents,  that  the 
stopple  adheres  so  firmly  as  to  resist  all  efforts  to  remove  it 
with  the  fingers.  It  is  then  necessary  to  tap  it  gently  and 
alternately  on  each  side  with  the  handle  of  a  spatula, — the 
spatula  being  held  by  the  blade,  and  the  bottle,  by  the  top 
of  its  stopple — the  body  resting  on  the  table,  in  the  other 


68  THE  LABORATORY — THE  TEST-CASE. 

hand.  In  ordinary  cases  this  process  loosens  the  stopper,  hut 
if  it  fails,  it  then  becomes  necessary  to  carefully  expand  the 
neck  over  the  flame  of  the  small  spirit  lamp,  and  in  order  that 
it  may  be  uniform,  the  bottle  must  be  kept  constantly  revolv- 
ing in  a  horizontal  position.  When  sufficient  warmth  has 
been  applied,  a  gentle  tapping  of  the  stopple,  as  above  directed, 
effects  its  removal.  After  the  neck  of  the  bottle  has  cooled, 
it  and  the  stopper  must  be  washed  and  dried  before  the  latter 
is  returned  to  its  place,  otherwise  it  will  soon  become  tightened 
again.  The  plan  sometimes  adapted  of  inserting  the  head  of 
the  stopper  in  a  chink  and  then  wrenching  it  out  as  it  were 
by  turning  the  bottle  with  the  hand,  is  not  ad\dsable,  as  it 
endangers  the  safety  of  both  the  vessel  and  hand. 

When  the  lamp  is  used,  the  motions  must  be  dexterous  and 
careful,  so  as  to  confine  the  heat  to  the  neck  of  the  bottle,  for 
if  it  is  allowed  to  reach  the  stopper  also,  the  expansion  of  both 
being  then  equal,  the  removal  of  the  former  cannot  be  effected. 
The  success  of  the  effort  depends  upon  a  difference  of  tempe- 
rature between  the  stopple  and  the  neck  which  encloses  it. 
Friction,  induced  by  drawing  a  string  constantly,  and  for  a 
length  of  time,  to  and  fro  around  the  neck  of  the  bottle,  is 
sometimes  substituted  for  the  heat  of  a  lamp. 

When  the  cementing  matter  is  a  crystallized  salt,  hot  water 
placed  around  the  edges  will  loosen  the  stopper  by  dissolving 
the  salt; — when  it  is  metallic  matter,  hydrochloric  acid  is 
necessary,  care  being  requisite  that  it  does  not  injure  the  con- 
tents of  the  bottle.  In  some  cases  olive  oil,  similarly  applied, 
is  more  effectual  than  either  hot  water  or  acid. 

These  remarks  are  equally  applicable  to  nearly  all  kinds  of 
closed  glass  vessels.  Broken  glass  and  odd  stoppers  being 
often  needed  for  various  uses,  should  be  preserved  in  a  box 
for  the  purpose. 

The  Test-case. — The  bottles  of  the  test-case  should  be  of 
white  glass,  entirely  free  from  lead,  and  nicely  fitted  with  ground 
stoppers.  As  they  are  constantly  in  use,  it  is  preferable  to  etch 
their  labels  upon  the  glass.  This  is  readily  done  by  the  ope- 
rator himself,  who  has  only  to  coat  a  limited  space  of  the 
bottle  (see  Fig.  36)  with  melted  wax,  and  after  tracing  thereon, 
with  an  iron  style,  the  name  and  symbol  of  the  reagents  to  be 
contained  therein,  to  wet  the  marks  with  sulphuric  acid,  and 
then  sprinkle  on  some  finely  powdered  fluoride  of  calcium 
(fluor  spar).    The  fluohydric  acid  thus  set  free  attacks  the  glass, 


THE  LABORATORY — THE  TEST  SERIES.         69 

and  renders  the  latter  opaque  and  distinct,  whilst  the  wax 
protects  the  other  portion  from  its  action,  and  when  removed, 
presents  the  smooth  surface  of  the  glass.  Care  should  be  taken 
to  avoid  contact  with  any  of  the  escaping  vapor,  as  it  is  dele- 
terious. 

When  paper  labels  are  used  they  must  be  payed  over  wdth 
a  thick  coating  of  insoluble  varnish,  and  written  upon  with 
incorrodible  ink.  The  former  consists  of  white  of  egg  (strain- 
ed), which  is  to  be  applied  with  a  camel's  hair  pencil,  and 
immediately  coagulated  by  steam  heat  and  then  dried  in  an 
oven  at  about  212°  F.  The  ink  is  made  by  dissolving  one 
part  of  genuine  asphaltum  in  four  parts  of  oil  of  turpentine, 
and  adding  lamp  black  to  render  it  properly  consistent.  The 
neatest  method  of  marking  the  labels  with  the  ink  is  by  means 
of  a  small  stamp  and  types.  When  the  ink  has  dried,  the  var- 
nish is  to  be  applied  as  above,  but  preferably  after  the  label 
has  been  pasted  (with  gum  tragacanth)  upon  the  bottle.  The 
transparent  film  hardened,  and  rendered  insoluble  by  heat, 
presents  a  firm  resistance  to  strong  acids,  alkaline  solutions 
and  other  reagents,  and,  moreover,  this  kind  of  label  is  eco- 
nomical. 

The  test  series  consists  of  eighty-two  bottles,  which  have  their 
position  in  the  case  over  the  operating  table.  Fig.  24.  Of  this 
series,  there  are  eighteen  narrow-mouthed  pints  with  contents 
as  follows: 


1  Sulphurous  acid  (in  solution) 

SO, 

2  Hydrochloric  acid  (common) 

HCl 

3             "                «     (pure) 

HCl 

4  Chlorine  water  (in  solution) 

Cl-fH 

5  Nitric  acid  (common) 

NO- 

6       "        "     (pure) 

NO, 

7  Sulphuric  acid  (common) 

SO, 

8           «           «    (pure) 

SO3 

9  Nitromuriatic  acid  (aqua  regia) 

NO.-fCl,HO 
KO4-HO 

10  Hydrate  of  potassa  (in  solution) 

1 1  Aqua  ammonia 

NH.O 

12  Carbonate  potassa  (in  solution) 

KO.CO. 

13           "         soda 

NO.CO. 
NH^O.CO 

14           "         ammoniae           " 

1 5  Acetate  of  lead          «         « 

PbO,A 

16  Sulphate  of  lime       "         " 

CaO,S03 

17  Lime  water 

CaO-f-HO 

18  Sulphuretted  hydrogen       " 

HS 

The  next  size  (narrow-mouthed)  is  eight  ounces,  and  of 
these  there  are  nineteen  with  liquid  contents,  as  follows: 


70 


THE  LABORATORY. 


19  Acetic  acid 

20  Oxalic    " 

21  Tartaric" 

22  Phosphorous  acid 

23  Ether 

24  Chloride  of  ammonium 

25  Hydrosulphuret  of  ammonia 

26  Oxalate  of  ammonia 

27  Chloride  barium 

28  Chloride  calcium 

29  Phosphate  soda 

30  Sulphate  copper 

3 1  Basic  acetate  of  lead 

32  Proto-sulphate  of  iron 

33  Sesqui-chloride  of  iron 

34  Sulphate  of  magnesia 

35  Sulphuret  of  Potassium 

36  Sulphate  of  alumina 

37  Infusion  of  galls 


C4H3O3  or  A 
C2O4,  H_ 

C8H,0,o=T 

PO^ 

C,H,0 

NH.Cl 

NH^S+HS 

NH^O,©" 

BaCl 

CaCl 

HO,2NaO,P05 

CuOjSOg 

3PbO;A 

FeO,S03 

Fej.CL 

MgO,!S034-HO 

KS, 


The  four  ounces  number  ten,  of  which  the  liquid  contents 
are  as  follows: 


38  Bitartrate  of  potassa 

39  Acetate      "        " 

40  Basic  silicate      " 

4 1  Chloride  of  mercury 

42  Protochloride  of  tin 

43  Proto-nitrate  of  mercury 

44  Chromate  of  potassa 

45  Sulphate  of  potassa 

46  Succinate  of  ammonia 

47  Borate  of  soda 


K0,H0,T 

KO,A 

3KO,Si3 

Hg,C]2 

Sn,Cl 

Hg,0,N05 

Ka0,Cr03 

KaO,S03 

NH,0,S=(C,H203) 

NaO/iBOg 


The  two  ounces,  eight  in  number,  contain  of  liquids  as  fol- 
lows: 

48  Bicarbonate  potassa  K0,2C0g 

49  Acetate  of  baryta  BaO,A 

50  Ferrocyanide  of  potassium  2KCfy 

51  Ferricyanide  of  potassium  K3,Cfy2 

52  Baryta  water  BaO-fHO 

53  Nitrate  of  silver  AgO,N05 

54  Iodide  of  potassium  KI 

55  Solution  of  indigo 

The  liquid  contents  of  the  one  ounce  test  bottles  are, 


56  Carbazotic  (nitropicric)  acid 

57  Nitrate  of  nickel 

58  Proto-nitrate  of  cobalt 

59  Nitrate  of  potassa 

60  Ammonio-nitrate  of  silver 


C,2H  N^0,3-f  Aq 

NiO,N05 

C0,N05 

K0,N05 
Ag0,N05-f2NH3 


THE  LABORATORY — THE  TEST  SERIES.  71 

6 1  Bichloride  of  platinum  Pt^Clg 

62  Chloride  of  gold  Au,Cl 

63  Caustic,  soda  Na,0 

64  Antimoniate  of  potassa  KOjSbOj 

65  Cyanide  of  mercury  HgjCy, 

In  addition  to  the  narrow-mouthed,  there  are  required  fifteen 
wide-mouthed  glass  stoppered  bottles,  The  contents  of  these 
are  as  follows: 

In  the  eight  ounces 


66  Mixture  of  carbonates  of  soda  and  potassa 

NaO,C02-fKO,CO, 

67  Carbonate  of  lime 

CaO,CO„ 

68  Sulphuret  of  iron 

FeS 

69  Dry  carbonate  of  soda 

NaO,CO,  (dry) 

70  Carbonate  of  baryta 

BaO,C02 

7 1  Cyanide  of  potassium 

KCy 

72  Granulated  zinc 

Zn 

73  Per-oxide  of  mercury 

HgO^ 

n  the  four  ounces ; 

74  Hydrated  oxide  of  bismuth 

BiO,+HO 

75  Oxide  of  lead 

PbO 

76  Blue  litmus  paper 

77  Red        "          " 

78  Turmeric         " 

79  Georgina          « 

80  Lead      " 

81  Starch  paste 

A  leaden  bottle  of  two  ounces  capacity,  for  the  hydrofluo- 
silicic  acid  3HF,-f-2SiF3  completes  the  series. 

All  these  bottles  should  be  made  heavy,  for  if  too  thin, 
being  so  frequently  handled,  they  are  liable  to  be  broken.  Of 
the  preceding  numbers,  1,  2,  3,  4,  5,  6,  T,  8,  9,  10,  11,  18, 
23,  25,  should  be  furnished  with  ground  glass  caps  as  shown 
by  Fig.  36;  No.  53  must  be  of  dark  glass  or  else  covered 
exteriorly  with  tin  foil.  Nos.  77,  78,  79,  80,  81,  should  always 
be  accompanied  with  a  pair  of  pincers  with  platinum  points 
similar  to  those  used  in  blowpipe  operations,  as  the  test  papers 
should  never  be  handled  with  the  fingers.  The  bottles  for 
alcohol  (C^HgOg),  and  distilled  water  (HO)  may  be  of  common 
green  glass,  narrow-mouthed  and  quart  sized.  They  are  fitted 
with  double  tubes  so  as  to  insure  a  gradual  egress  of  the 
liquid;  and  are  designed  as  conveniences  to  the  operating 
table,  for  supplying  small  quantities  of  their  contents  to  test 
tubes  and  narrow-mouthed  vessels  without  the  aid  of  a  funnel. 
Fig.  38  shows  their  form  and  arrangement. 


72      '  THE  LABORATORY. 

A  piece  of  bright  copper  and  one  also  of  iron  are  also  fre- 

quently  needed  as  reagents. 
^^*     ■  All  of  the  forenamed  reagents  must  be  chemically 

pure,  as  also  the  water  used  in  making  solutions  of 
them.  The  processes  by  which  they  are  prepared, 
would  not  be  altogether  inappropriate  to  this  work, 
but  more  pertinent  matter  demands  our  space  and 
so  we  refer  the  operator  to  an  excellent  treatise  upon 
the  subject,  by  Mr.  E.  N.  Kent,  practical  chemist 
of  New  York,  and  now  in  the  progress  of  prepara- 
tion for  the  press. 
Besides  these  reagents,  a  small  stock  of  which  should 
always  be  kept  in  reserve  on  the  shelves  of  the  cupboard, 
there  is  required  a  general  assortment  of  drugs  and  chemicals 
in  limited  quantity.  The  coarser  and  cheaper  articles  of  this 
stock  should  preferably  be  purchased  from  the  dealers,  but  it 
is  advisable  for  the  operator  to  prepare  the  costlier  ones  for 
himself,  not  only  on  the  score  of  economy,  but  also  because 
of  the  practice  which  he  will  acquire  in  the  manipulations  of 
various  processes. 

There  remain  but  few  points  to  be  remarked  upon  before 
closing  our  chapters  upon  the  laboratory.  We  have  already 
enjoined  upon  the  experimenter,  great  cleanliness,  and  we 
now  repeat  the  injunction.  The  hands  should  always  be  free 
from  dirt,  and  invariably  washed  with  castile  or  palm  soap 
before  going  to  meals.  This  precaution  is  absolutely  neces- 
sary on  account  of  health,  for  otherwise,  in  working  with 
deleterious  matters,  the  little  particles  which  secrete  them- 
selves under  and  around  the  finger  nails,  may  be  conveyed 
into  the  system  and  thereto  work  an  injury.  So  also,  when 
engaged  at  one  time  upon  several  operations  of  a  difi'erent 
nature,  it  is  necessary  to  rinse  the  hands  in  passing  from  the 
management  of  one  to  that  of  another  of  them.  For  this 
purpose,  the  hydrant  or  reservoir  with  its  adjoining  hand- 
towel,  Fig.  22,  is  very  convenient. 

To  protect  the  person  from  dirt,  the  operator  should  pro- 
vide himself  with  a  suitable  costume.  A  long  wrapper  of 
linsey  or  baize  for  winter,  and  of  Holland  linen  for  summer, 
is  very  suitable.  A  light  cap  of  some  cheap  material,  is  a 
good  shield  to  the  hair  against  the  bad  effects  of  dust  and 
vapor. 

In  all  investigations,  the  practice  of  working  upon  small 


THE  LABORATORY — RECORD  OF  ANALYSES.  73 

quantities,  will  lead  to  habits  of  nice  and  delicate  manipula- 
tion. Besides,  it  is  easier,  less  costly  and  fatiguing  to  manage 
a  small  portion  of  any  substance.  Record  your  processes  in 
the  laboratory  book,  to  be  kept  specially  for  the  purpose; — 
note  in  detail  the  modus  operandi  pursued,  and  the  results 
with  the  day  and  date,  so  that  you  may  have  every  facility  of 
drawing  a  clear  conclusion  from  the  results  of  your  labors. 

There  are  two  other  books  needed,  one  is  the  Record  of 
Analyses,  in  which  are  transcribed  the  analyses  of  such  sub- 
stances as  may  undergo  examination  in  the  laboratory.  Their 
mode  of  analysis  may  also  be  annexed.  This  record  is  very 
useful  for  future  reference.  The  other  book  is  an  ''Index 
rerum'  after  the  plan  of  the  Rev.  J.  Todd,  author  of  the 
Student's  Manual.  As  it  is  impossible  to  retain  in  the  memory 
all  that  one  reads  or  sees  in  the  numerous  works  which  come 
under  his  eye ;  and  as  we  meet  with  much  that  is  valuable, 
and  really  worth  preserving,  we  must  resort  to  some  other 
means  more  practicable  and  less  laborious  than  copying  out 
extracts.  Mr.  Todd  recommends  the  habit  of  making  an 
index  rerum  of  reading.  This  book  consists  of  several  quires 
of  blank  sheets,  letter  form,  and  is  alphabetically  classified, 
so  as  to  exhibit  at  a  glance,  the  name  of  the  book  and  the 
number  of  the  page  treating  of  the  subject,  the  synopsis  of 
which  is  recorded  under  its  appropriate  letter  and  heading. 
There  are  many  facts  and  opinions  met  in  reading,  especially 
in  the  journals,  which  are  certain  to  be  wanted  some  day  or 
other,  and  by  thus  gradually  storing  up  you  save  yourself  a  deal 
of  trouble  for  the  future  when  there  is  need  of  research  upon 
any  subject;  and  in  a  few  years  will  have  accumulated  a  mass 
of  information  of  incalculable  value  in  the  practice  of  your 
profession.  Always,  as  Mr.  Todd  directs,  have  your  index 
at  hand  when  reading  book,  journal,  pamphlet,  or  newspaper; 
and  "when  you  meet  with  anything  of  interest,  note  it  down, 
the  subject,  the  book,  the  volume,  and  the  page;  and  make 
your  index  according  to  subjects  as  much  as  possible,  selecting 
that  word  for  the  margin  which  conveys  the  best  idea  of  the 
subject,"  so  that  there  may  be  no  difficulty  in  finding  the 
original  place  when  it  is  necessary  to  refer  to  it.  For  example, 
in  reading  the  journals  for  this  year,  you  find  several  articles 
which  you  may  wish  to  refer  to  again,  and  so  note  down  their 
subject  matter  as  follows: 


74 


THE  LABORATOKY — INDEX  RERUM. 


ACIDS  FATTY. 


G 

GUN  COTTON. 

S 
SUGAR. 


Their  constitution^  new  theory  of^  hy 
Jas.  C.  Booth,  Journal  of  the  Franklin 
Institute  for  1848. 


Different  views   of  its   composition. 
Encyclopoedia  of  Chemistry,  p.  488. 


Analyses  of  hy  circular  polarized 
light,  Report  to  Congress  hy  Professor 
B,  S,  M'CulloL  1847. 


There  are  many  other  minutiae  that  might  be  mentioned,  but 
for  want  of  room  for  more  important  matter;  they  will,  how- 
ever, suggest  themselves  in  the  progress  of  operations. 

Habits  of  industry,  close  observation  and  neatness,  are  in- 
dispensable to  the  acquisition  of  a  proficiency  in  manipulation, 
without  which  it  will  be  difficult  to  form  correct  conclusions. 

The  laboratory  which  we  have  described,  is  well  appointed 
for  every  branch  of  research.  Many  of  the  implements  enu- 
merated may  be  dispensed  with  for  ordinary  operations,  but 
they  are  requisite  for  a  complete  arrangement,  which,  as 
given  in  the  preceding  chapters,  is  not  at  all  extravagant. 
Moreover,  with  a  little  extra  industry,  the  operator  can  soon 
realize  the  outlay  for  all  conveniences,  in  the  manufacture 
and  sale  of  such  pure  chemicals  as  may  be  in  demand.  We 
have  provided  him  with  every  appliance  for  the  purpose,  so 
that  his  self  improvement  may  be  attended  also  with  pecuniary 
profit. 

Where  the  means  are  limited,  it  is  better  that  the  purchase 
of  apparatus  should  be  gradual,  commencing  with  those  pieces 
which  are  of  most  general  use.  This  course  judiciously  car- 
ried out,  will  in  time  possess  the  owner  of  a  well  stored  labo- 
ratory. All  stock  and  apparatus  can  be  bought  from  the 
manufacturer,  or  importer,  at  very  little  over  one-half  the 
dealer's  prices,  for  the  same  articles. 


DIVISION — SLICING — CONTUSION. 


75 


CHAPTER   IV 


DIVISION  OF  SUBSTANCES. 


This  operation  is  a  mechanical  process,  by  which  the  sur- 
face and  points  of  contact  of  solid  bodies  are  multiplied; 
thus  diminishing,  in  a  high  degree,  the  opposing  force  of 
cohesion ;  and,  consequently,  by  promoting  greater  access  to 
its  particles,  enabling  the  more  ready  and  rapid  action  of  re- 
agents upon  solid  matter. 

The  means  by  which  the  division  of  solid  matters  is  accom- 
plished are  manifold,  and  vary  with  the  nature  of  the  sub- 
stance to  be  reduced ;  some  bodies  being  pulverizable  by  almost 
any  of  the  processes,  while  others  again  require  a  particular 
method  for  their  reduction.  The  different  modes  of  operating 
may  be  classified  as  follows : — 

1st.  Slicing. — This  process  applies  to  fibrous  matters,  and 
is  practised  with  a  lever-knife,  similar  to  that  used  by  tobac- 
conists for  cutting  tobacco,  and  shown  by  Fig.  39. 

Fig.  39. 


Being  thus  reduced  to  thin  slices,  the  substance  is  in  better 
form  for  maceration,  &c. ;  and,  moreover,  admits  of  readier 
desiccation,  a  necessary  process  when  it  is  required  to  be  further 
reduced  under  the  pestle,  or  by  being  grated  on  a  coarse  rasp. 

This  mode  of  pulverization  by  rasping,  though  particularly 
applicable  to  fibrous  substances,  such  as  fresh  roots  and  the 
like,  is  sometimes  used  for  metals  and  hard  matters.  In  the 
latter  case,  the  files  must  have  finer  and  sharper  teeth,  and  in 
both  instances  be  perfectly  clean,  and  free  from  grease  and  dust. 

2d.  Contusion. — In  order  to  attain  a  minute  division  of  the 
denser  substances,  whose  particles  are  very  cohesive,  resort 
must  be  had  to  the  pestle  and  mortar.    The  material  of  this  ap- 


<f 


76  DIVISION — MORTARS.  t 

paratus  varies  with  the  nature  of  the  substance  to  be  powdered. 
To  prevent  errors,  corrosive  or  caustic  matter  should  never  be 
pulverized  in  metallic  mortars,  else  by  a  solution  of  a  portion, 
or  contamination  with  abraded  particles,  unavoidable  confusion 
will  ensue.  The  resistant  nature  of  the  material  of  the  mortar 
must  be  proportional  to  the  hardness  of  the  body  to  be  ope- 
rated upon.  For  the  harder  insoluble  substances,  those  of 
iron,  brass,  or  steel  are  generally  used.  For  the  less  dense 
and  more  pulverizable  bodies,  especially  those  which  are  acid> 
or  corrosive,  porcelain,  wedge-wood  or  glass  is  the  proper  mate- 
rial. Marble,  being  readily  attacked  by  acids,  mortars  of  that 
material  are  only  used  for  reducing  those  inert  substances  which 
are  readily  comminuted  merely  by  trituration,  such  as  chalk, 
neutral  salts,  &c.  This  material,  as  well  as  glass,  is  well 
replaced  by  porcelain  or  wedge-wood,  which  are  stronger,  and 
otherwise  much  less  objectionable.  There  should  be  an  as- 
sorted series  of  mortars  for  laboratory  purposes. 

The  large  iron  mortar  has  its  position  in  the  furnace-room, 
and  is  permanently  and  firmly  fitted  upon  a  block,  in  some 
convenient  place,  for  general  use,  in  pounding  ores,  metals, 
and  coarser  substances.  The  pestle  of  this,  as  of  all  other 
mortars,  should  invariably  be  of  one  piece  and  of  the  same 
material  as  the  mortar;  because,  when  the  lower  part  is  fitted 
to  a  handle,  it  is  apt  to  become  loosened  and  drop  off  particles 
of  the  cement  with  which  it  is  fastened,  to  the  injury  of  the 
contents  of  the  mortar.  The  handle  or  upper  portion  must 
afford  convenient  space  for  grasping,  and  the  base  or  lower 
portion,  roughened  on  its  face  by  use  of  sand,  should  diverge  to 
a  diameter  of  about  one-fourth  of  that  of  the  mouth  of  the 
mortar.  Fig.  40  exhibits  a  mortar  of  proper  form  and  pro- 
portionate thickness  as  to  its  different 
Fig.  40.  parts.     Its  interior  form  is  nearly  that 

of  the  butt  end  of  an  egg,  so  as  to  pro- 
mote a  constant  contact  of  the  matters 
being  contused  with  the  rotating  pestle. 
To  prevent  the  ejection  of  particles  of 
matter  and  the  escape  of  dust,  and  con- 
sequent inconvenience  to  the  operator, 
as  the  case  may  be,  the  mortar  should  be 
provided  with  a  sheep  skin  conical  cover- 
let, with  a  hole  in  its  centre  for  the 
passage  of  the  pestle,  which  is  to  be 
fastened   around  its   rim  and  over  its 


DIVISION — MOKTARS.  77 

mouth,  with  a  string.  Circular  pasteboard  and  wooden  covers, 
of  sizes  corresponding  with  the  mortars  and  with  a  hole  in  their 
centres,  are  often  substituted  for  the  conical  coverlet.  The 
operator  should  always  stand  with  his  back  to  a  current  of 
air  ;  and  to  further  guard  against  the  unpleasant  or  deleterious 
effects  of  the  fine  dusty  particles  which  may  arise  from  the 
mortar,  he  can  moisten  its  contents  with  a  little  water,  pro- 
vided that  liquid  is  without  action  upon  the  substance.  Ex- 
posure to  warmth,  for  the  evaporation  of  the  water,  will  restore 
the  matter  to  its  original  dryness. 

All  substances  formed  of  an  organic  tissue  should  be  pre- 
viously dried,  so  as  to  afford  greater  facility  in  their  pulveri- 
zation. A  previous  reduction  of  ores,  and  coarse  hard  sub- 
stances into  lump,  by  concussion  with  a  hammer  upon  an 
anvil,  and  of  roots  and  the  like  into  slices  or  bits  with  a  com- 
mon knife  or  lever  cutter,  (Fig.  39,)  are  preliminary  processes 
which  greatly  facilitate  their  pulverization.  The  substance 
to  be  struck  upon  the  anvil  should  be  previously  wrapped  in 
strong  brown  paper. 

Silicious  stones  pulverize  much  more  readily  after  having 
been  heated  to  redness  in  a  crucible,  and  in  that  state  pro- 
jected into  cold  water.  This  increased  friability  is  occasioned 
by  the  unequal  cooling  of  the  mass. 

Metals,  alloys  and  the  like,  which  are  difficultly  pulveri- 
zable  whilst  cold,  may  also  be  readily  crushed  when  heated  to 
redness. 

When  it  is  required  to  reduce  the  substance  into  small 
fragments  only,  it  can  be  broken  down  by  a  succession  of 
blows  with  the  pestle.  If  the  substance  is  very  hard,  the  force 
of  the  arm  should  be  added  to  the  descending  weight  of  the 
pestle,  so  as  to  impart  power  to  the  blow.  A  subsequent 
circular  grinding  motion  of  the  pestle,  continued  for  a  length 
of  time  will  further  reduce  these  fragments  to  fine  powder, 
and  consequently  this  movement  must  be  avoided  when  only 
a  coarse  comminution  is  desired.  The  mortar  must  always 
rest  upon  a  solid  foundation,  and  during  the  operation  of 
pounding  should  be  occasionally  shaken,  in  order  that  the 
coarser  particles  which  mount  to  the  sides  may  be  forced  back 
to  the  centre  of  the  mortar ;  so  as  to  receive  the  full  effects  of 
the  descending  pestle,  which  should  never  be  allowed  to  strike 
the  sides  of  the  mortar.  If  the  substance  is  to  be  reduced  to 
a  fine  powder,  the  process  is  greatly  facilitated  by  operating 


78 


DIVISION — MORTARS. 


upon  only  a  small  portion  at  a  time,  as  the  pestle  is  less  liable 
to  become  clogged. 

In  the  analysis  of  rare  minerals,  especially  those  which  are 
very  hard,  the  reduction  is  effected  in  a  small  mortar  of 
hardened  steel.     This  apparatus,  shown  by  Fig.  41,  consists 

Fig.  41. 


O 


(■■ 

A 

I 

'^   1 

of  three  separable  pieces,  each  of  which  is  smoothly  turned,  so 
as  to  present  an  even  surface  exteriorly  and  interiorly.  0 
is  the  base  piece  into  the  cavity  of  w^hich  the  cylinder  B  fits 
somewhat  loosely.  It  is  this  cylinder  which  receives  the 
mineral  to  be  reduced.  Sliding  into  it  is  the  exactly  fitting 
pestle  A^  which  being  struck  successively  with  a  hammer, 
crushes  the  mineral  to  powder  without  waste  of  any  of  its  par- 
ticles by  ejection. 

When  the  powder  thus  obtained  is  not  yet  sufficiently  fine 
for  analysis,  it  must  be  transferred  to  an  agate  mortar,  and 
rubbed  with  the  pestle  until  reduced  to  an  impalpable  state. 
The  pestle  and  mortar  are  of  the  same  material,  the  hardness 
and  smoothness  of  which  render  it  particularly  applicable  for 
the  purpose.  The  motion  of  the  pestle  should  always  be  cir- 
cular, otherwise  a  perpendicular  blow  may  endanger  the  safety 
of  the  mortar,  especially  if  it  has  a  fissure,  as  is  often  the 
case,  running  through  it.  The  given  w^eight  of  the  mineral 
for  analysis  must  always  be  estimated  after  pulverization; — 
never  previously,  lest  a  loss  by  ejection,  or  adhesion  to  the 
mortar,  or  spatula  may  lead  to  inexact  results.     Fig.  42  ex- 


TRITURATION — PORPHYRIZATION.  79 

hibits  an  agate  mortar,  which  can  be  purchased 

of  sizes  varying  from  1  to  6  inches  in  diameter.        Fig.  42. 

One  of  about  3J  inches  width  will  be  most  useful. 

It  should  be  selected  as  free  from  indentations, 

fissures  or  cavities  as  possible,  for  these  faults  not 

only  impair  the  durability  of  the  mortar,  but 

render  its  cleansing  very  difficult. '    An  excellent 

plan  of  removing  tenaceously  adhering  matter  from  the  sides 

or  bottom  of  a  mortar,  is  to  rub  them  with  pumice  stone  and 

water. 

3d.  Trituration. — This  mode  of  manipulating  with  the  pestle 
is  applicable  to  those  substances  which  are  friable,  and  fall  to 
powder  by  being  merely  rubbed  up  by  a  circular  or  grinding 
motion  of  the  pestle,  and  which  would  soften  and  become  ob- 
stinate by  being  pounded.  Chalk  and  the  like,  and  most  of 
the  salts  are  in  the  first  category ; — the  resins  and  gum  resins 
in  the  second. 

Sand  is  added  to  facilitate  the  reduction  of  resins  and 
similar  substances,  which  cake  under  the  pestle,  only  when 
they  are  intended  for  maceration  or  solution.  Under  other 
circumstances,  the  medium  would  be  an  adulterant  on  account 
of  the  impossibility  of  separating  it. 

The  proper  material  for  a  mortar  for  this  purpose  is  white 
wedge-wood,  of  form,  as  shown  by  Fig.  43.  Berlin  porcelain 
mortars,  glazed  outside  and  biscuit  internally,  with  broad  but- 
ted, solid  pestles,  as  shown  at  Fig.  44,  are  neat  and  convenient 

Fig.  43.  Fig- 44. 


implements,  but  less  available  for  general  purposes  than  those 
of  wedge-wood,  which  are  stronger,  more  durable,  and  will 
stand  harder  blows.  These  are  purchased  by  the  diametral 
inch,  and  the  most  convenient  size  is  6  to  8  inches  width  at  the 
mouth.  It  will  be  well  also  to  have  a  smaller  one  of  the  same 
material,  say  of  2  inches  diameter  at  the  top. 

4th.  Porphyrization. — This  mode  of  pulverization,  only  em- 
ployed when  it  is  desired  to  give  the  comminuted  substance  the 


80  ,    PORPHYRIZATION — SIFTING. 

greatest  fineness,  takes  its  name  from  that  of  the  material  of  the 
vessels  in  which  it  is  practised.  A  small  porphyry  mortar,  hemi- 
spherical interiorly,  or  preferably  a  slab  and  muller  is  the 
apparatus  employed.  Flint  and  even  glass,  which  are  equally 
as  hard  as  porphyry,  form  an  economical  substitute  for  that 
material.  It  is  highly  important  that  the  material  of  the  ap- 
paratus shall  be  less  easily  abraded  than  the  substance  being 
ground;  for  if  too  soft,  the  latter  becomes  contaminated  with 
the  particles  which  are  rubbed  off,  and, 'hence,  in  exact  investi- 
gations, inaccuracy  is  caused. 

Porphyrization  is  generally  effected  by  rubbing  the  coarse 
powder  between  a  flat  slab  and  muller,  until  reduced  to  an 
impalpable  state.  The  circular  motion  of  the  muller  disperses 
the  powder  over  the  slab,  rendering  it  frequently  necessary  to 
collect  it  together  in  the  centre  with  a  spatula,  so  as  to  keep 
it  uniformly  under  the  action  of  the  muller.  The  spatula  may 
be  of  horn  or  steel,  but  is  better  when  of  platinum.  Fig.  45 
exhibits  a  slab  and  muller.  When  the 
Fig-  45.  substance  under  operation  is  unalterable 

by  water,  it  may  be  moistened  with  that 
liquid,  which,  by  converting  it  into  a 
paste,  facilitates  its  reduction  and  pre- 
vents any  waste  by  the  escape  of  dusty 
particles.     The  powdered  paste  is  easily 
dried  by  being  dropped  in   dots  upon  a  porcelain  plate  and 
exposed  to  warmth.     Those  matters  which  are  soluble  in  or 
alterable  by  water,  must  be  porphyrized  in  a  dry  state. 

5th.  Sifting. — The  impossibility  of  reducing  the  whole  of  a 
substance  at  once  to  a  uniform  state  of  fineness  by  any  of 
the  preceding  processes,  renders  necessary  an  occasional  sepa- 
ration, during  the  progress  of  pulverization,  of  the  more  com- 
minuted portions  from  the  grosser  particles.  This  is  effected 
by  means  of  a  sieve,  of  which  there  should  be  several  in  the 
laboratory.  A  wooden  cylinder  of  about  four  inches  depth, 
with  an  accompanying  ring  of  the  same  materials,  constitutes 
the  frame,  over  which  can  be  stretched  a  cloth  of  any  required 
fineness.  For  coarser  articles,  fine  brass  wire  is  the  best 
material  for  the  cloth,  but  when  the  powder  is  to  be  impal- 
pable, bolting  cloth  (raw  silk),  or  gauze  is  requisite.  Sieves 
are  also  covered  with  hair-cloth,  buckram,  book-muslin,  and 
iron  wire  of  different  sized  meshes,  each  of  which  has  its  ap- 
propriate application.     The  metallic  sieves  should  have  their 


a 


I  HIIIIII'ilIM 


SIFTING — SIEVES. 


81 


JWi 

\m\U'. 

Hl^illllMI 

■ 

Iiliiii  ■  ■ 

"iiiiliiliiii 

il'i" 

'fii'ii 

|i'i!i""'i'!ll 

[jLr- 

:-h 

,;\!/:l::l 

cloths  permanently  fitted  to  them.  For  all  the  rest,  two 
frames,  as  above  described,  one  of  much  larger  dimensions 
than  the  other,  will  serve ;  as  it  is  only  necessary  to  remove 
the  ring  when  it  is  desired  to  substitute  one  kind  of  covering 
for  another.  The  sieves  of  cloth,  of  graduated  fineness,  can 
be  kept  in  some  secure  place,  and  withdrawn  as  wanted,  and 
thus  we  have  the  economical  means  of  possessing  a  full  suite 
of  sieves  from  the  metallic  wire,  through  all  the  grades  of 
fineness  up  to  the  closest  wrought  bolting-cloth.  The  form 
of  a  sieve  is  shown  at  A,  Fig.  46.  After  the  separation  of 
the  finer  portions  by  the  sieve,  the 
coarser  particles  are  again  subjected  Fig-  46. 

to  grinding  and  sieving  as  often  as  is 
necessary  to  convert  the  whole  into 
the  requisite  state  of  uniform  fineness. 

Horn  scoops  or  porcelain  spoons  or  ifaiiiiriiriri.^  ^' "  ^  ^llllll^illllal .^ 
ladles  are  the  proper  implements  for 
transferring  the  contents  of  the  mor- 
tar to  the  sieve.  In  some  cases  a  stifi" 
pasteboard  card,  being  more  pliable, 
is  a  convenient  substitute.  The  use 
of  the  hand,  for  this  purpose,  should  always  be  avoided  as  a 
slovenly  practice.  A  platinum,  horn  or  bone,  or,  less  pre- 
ferably, steel  spatula  may  be  used  to  detach  the  particles  ad- 
herent to  the  sides  of  the  mortar.  To  prevent  inconvenience 
or  injury  to  the  operator,  (who,  both  in  powdering  and  sieving, 
should  always  stand  with  his  back  to  a  current  of  air,)  from 
particles  of  dust  or  acrid  poisonous  matter,  as  well  also  to 
avoid  waste,  the  sieve  should  be  fitted  with  a  top  and  bottom 
covering,  as  shown  at  B  and  (7,  in  Fig.  46,  the  upper  of  which 
arrests  the  escape  of  the  light  dust  into  the  air  and  the  lower 
receives  that  portion  which  passes  through  the  cloth.  These 
covers  are  headed  with  parchment  or  calf-skin,  and  the  three 
divisions,  when  joined  together,  form  what  is  called  a  drum  or 
box  sieve.  The  powder  is  made  to  pass  through  the  meshes 
by  gently  agitating  the  sieve  between  the  hands.  A  rough 
jarring  motion  will  force  through  some  of  the  coarser  par- 
ticles, and  thus  destroy  the  uniformity  of  the  powder,  and 
hence  the  common  practice  of  tapping  it  fi-equently  against 
the  side  of  the  mortar  should  be  abandoned,  unless  the  state 
of  fineness  is  immaterial.  Some  substances,  however,  as  mag- 
nesia, &c.,  which  obstruct  the  pores  of  the  cloth,  must  be 


82  LEVIGATION — ELUTRIATION. 

forced  through  in  this  manner,  and  even,  if  necessary,  by  a 
circular  motion  of  the  fingers  over  the  interior  surface  of  the 
cloth.  This  manipulation  frees  the  meshes  of  the  cloth  from 
obstructions,  but  it  must  be  carefully  done,  otherwise  the  safety 
of  the  cloth  will  be  endangered.  A  sieve  is  also  useful  for  the 
admixture  of  powders  of  uniform  fineness. 

6th.  Levigation — is  that  mode  of  mechanical  reduction 
which  is  practised  by  first  rubbing  the  substance  into  a  smooth 
paste,  and  then  separating  the  finer  from  the  coarser  portions, 
by  agitating  the  bruised  matters  with  water.  After  a  sufii- 
cient  repose,  the  grosser  and  heavier  portions  subside,  leaving 
the  lighter  particles  still  suspended  in  the  water.  This  water, 
after  decantation,  gives  a  second  deposit  of  an  increased  state 
of  tenuity.  The  third  or  fourth  decantation  yields  the  pow- 
der of  impalpable  fineness.  The  time  of  repose  between  the 
decantations,  unless  great  impalpability  is  required,  should  be 
limited,  and  only  long  enough  to  allow  the  deposition  of  the 
heavier  portions.  The  coarse  precipitates  are  collected  together, 
second  and  as  many  more  times  as  necessary,  rubbed  up  as 
before,  and  treated  with  water,  until  all  the  lighter  portions 
have  been  separated.  This  process  applies  only  to  substances 
unalterable  by  water.  When  uniformity  of  fineness  is  not  all 
important,  one  washing  even  sufiices,  and  can  be  accomplished 
in  the  mortar  without  the  use  of  glasses.  Alternate  pound- 
ings and  washings  will  eventually  reduce  and  remove  the  whole 
contents  of  the  mortar.  In  washing  over  gold  and  other  me- 
tallic ores,  where  only  the  heavier  portions  are  to  be  reserved, 
the  water  may  be  allowed  to  flow  directly  into  the  mortar, 
which  being  held  in  an  inclined  position,  permits  its  exit, 
together  with  the  fine  dusty  portions  which  are  kept  in  sus- 
pension by  trituration  with  the  pestle. 

This  process  of  levigation  is  founded  upon  the  difi'erent 
specific  gravities  of  the  coarse  and  fine  bruised  matters,  and 
is,  therefore,  not  only  applicable  for  the  separation  of  the 
particles  of  homogeneous  matters,  but  also  of  equally  fine  mat- 
ters of  unequal  densities.  In  the  latter  case  it  takes  the  name 
of  elutriation. 

All  minerals  for  analysis,  which  have  to  undergo  ignition 
with  alkalies,  should  be  previously  levigated,  in  order  that 
decomposition  may  be  complete;  for  if  the  powder  is  not  uni- 
form the  larger  particles  will  escape  decomposition. 

Pulverization  in  this  manner,  by  uniformly  comminuting 


GRANULATION — DIVISION  BY  INTERMEDIA.  83 

the  particles,  promotes  their  equal  expansion  and  the  escape 
of  contained  moisture,  and  thus  prevents  the  decrepitation  of 
substances  when  heated. 

The  deposited  powder  must  always  be  dried,  by  exposure, 
previous  to  subjecting  it  to  any  other  process. 

7th.  Reduction  hy  G-ranulation. — The  reduction  of  metals 
to  a  pulverulent  state  is  effected  by  fusing  them  in  a  crucible, 
and  pouring  the  melted  matter,  from  an  elevation,  in  a  thin 
stream,  very  gradually,  into  a  bulk  of  cold  water,  which 
is,  during  the  process,  kept  in  constant  agitation  with  a 
stirrer.  The  fineness  of  the  resultant  granules  is  proportional 
to  the  slowness  with  which  the  fused  metal  was  poured  into 
the  water.  It  is  more  convenient  to  transfer  the  metal  from 
the  crucible  into  a  ladle,  and  project  it  into  the  water  from 
that  more  handy  vessel,  which  enables  a  frequent  change  of 
the  position  of  the  descending  stream,  and  thus  prevents  the 
formation  of  clots  instead  of  smaller  and  more  solid  granules. 
The  fusion  of  zinc  for  granulation  must  be  in  a  covered  cru- 
cible, otherwise  it  becomes  oxidized  whilst  hot,  and  partially 
sublimes  by  exposure  in  an  open  vessel.  Zinc  may  also  be 
finely  divided  by  being  beaten,  whilst  hot,  in  a  heated  mortar. 

The  process  of  fusing  metals  and  then  agitating  the  melted 
matter  in  a  wooden  box  until  cool,  reduces  them  to  a  state  of 
minute  division,  but  at  the  same  time  promotes  their  oxidation. 
For  general  purposes,  however,  it  is  not  objectionable,  and  the 
particles  of  charred  wood  with  which  it  becomes  mixed  can  be 
separated  by  elutriation.  The  sides  of  the  box  are  generally 
well  chalked,  to  prevent  any  adherence  of  the  metal; — this 
also  is  separable  by  elutriation. 

REDUCTION   BY  CHEMICAL   MEANS. 

8th.  Division  hy  Intermedia. — This  mode  is  both  mechani- 
cal and  chemical,  and  applies  particularly  to  the  noble  metals, 
in  foil,  which  are  difficult  of  pulverization.  Honey,  sugar, 
salts,  &c.,  are  the  most  usual  media.  By  binding  the  parti- 
cles together,  it  assists  their  minute  division,  and  prevents 
their  escape  from  the  mortar.  The  addition  of  boiling  water 
solves  out  the  medium,  without  action  upon  the  metallic  pow- 
der, which  then  only  requires  to  be  thrown  upon  a  filter  and 
dried. 

Phosphorus  may  be  finely  divided  by  fusing  it,  with  alcohol, 


84  REDUCTION  BY  CHEMICAL  MEANS. 

over  a  water-batli,  and  shaking  the  contents  of  the  flask  until 
thoroughly  cooled.  The  phosphorus  subsides  at  the  bottom  in 
pulverulent  form.  Camphor,  which  is  obstinate  under  the 
pestle,  readily  yields  to  its  power  when  mixed  with  a  few 
drops  of  alcohol  or  ether,  to  destroy  its  elasticity. 

Silica  may  be  precipitated  from  lime  glass  in  a  pulverulent 
form,  by  the  digestion  of  that  compound  with  hydrochloric 
acid.  Silver  is  obtained  in  a  powder  by  the  decomposition  of 
its  nitric  solution  with  a  metallic  copper  rod ;  or  of  its  chloride 
by  metallic  zinc.  Proto-sulphate  of  iron  throws  down  gold,  in 
a  finely  divided  state,  from  the  solution  of  its  muriate;  and 
spongy  platinum  is  formed  by  the  dull  ignition  of  the  ammo- 
nia-muriate of  that  metal.  These  are  instances  of  chemical 
division  by  purely  chemical  means.  The  extreme  state  of 
division  thus  obtained  by  the  solution  and  precipitation  of  a 
solid  body  (and  also  by  fusion,  a  chemico-mechanical  process), 
cannot  be  effected  by  any  purely  mechanical  power. 

The  sublimation  of  sulphur  into  flowers,  as  also  of  calomel 
into  fine  powder  by  means  of  large  airy  chambers,  are  instances 
of  comminution  by  chemico-mechanical  means ; — the  vaporized 
particles  being  prevented  from  reunion,  at  the  moment  of 
solidification,  by  the  intervention  of  the  cold  air.  So,  like- 
wise, in  cases  of  division  by  hydro-sublimation,  the  interven- 
tion of  aqueous  vapor  prevents  the  conjunction  of  the  vapor- 
ized molecules.  Dr.  Joslin  {Sillimans  Journal^  p.  48,  vol. 
V.)  treats  of  this  subject  in  extenso. 


CHAPTER   Y. 

THE   BALANCE. 

A  BALANCE  may  be  considered  the  most  indispensable  im- 
plement of  the  laboratory,  as  affording  the  only  means  by 
which  the  chemist  can  accurately  estimate  the  quantitative 
results  of  his  investigations.  The  construction  of  this  in- 
strument for  determining  the  relative  weight  {the  measure 
of  the  force  hy  which  any  body,  or  a  given  portion  of  it,  gra- 
vitates towards  the  earth)  of  substances,  is  based  upon  certain 


THE  BALANCE — ITS  REQUISITE  CONDITIONS.  85 

mechanical  principles,  of  which  we  proceed  to  give  a  brief 
explanation. 

A  balance  consists  of  an  upright  shaft,  supporting,  by  its 
immediate  centre,  an  inflexible  lever  or  beam,  with  arms  of 
equal  length  and  symmetry,  to  each  of  which  is  suspended  a 
dish  for  the  reception  of  the  weights  (the  power),  and  the  body 
to  be  weighed  (the  resistance).  Of  the  three  axes  of  the  beam, 
that  in  the  middle  is  the  fulcrum  or  centre  of  motion,  upon 
which  it  turns  in  a  vertical  plane.  The  other  two  axes  are  at 
the  extremities  of  the  arms.  All  three  axes  should  be  at  right 
angles  to  the  plane  of  motion,  and  parallel  to  each  other. 

The  requisite  conditions  of  a  good  balance. — One  of  the 
chief  conditions  of  an  accurate  balance  is  a  free  suspension  of 
the  beam,  in  order  that  it  may  vibrate  with  the  least  possible 
friction.  The  two  arms  must  also  be  precisely  equal,  so  that 
when  empty,  or  the  weight  in  each  dish  is  uniform,  there  will 
be  a  perfect  equilibrium.  The  sensibility  of  a  balance  is  pro- 
portional to  the  angle  formed  by  the  beam  with  the  horizon, 
when  a  slightly  greater  weight  is  placed  in  one  dish  than  in 
the  other.  This  sensibility  depends  on  the  position  of  the 
centre  of  gravity  of  the  beam  with  reference  to  the  line  of 
suspension;  this  centre  must  be  below  that  line,  but  as  near 
as  possible  to  it,  so  that  the  slightest  weight  will  cause  the 
beam  to  oscillate  freely. 

As  the  inertia  and  friction  are  proportional  to  the  weight  of 
the  beam,  it  must  be  made  of  material  entirely  free  from  im- 
perfections, and  so  as  to  combine  strength  and  inflexibility 
with  lightness.  It  may  be  of  solid  steel,  rolled  brass,  German 
silver,  or  of  a  malleable  alloy  of  copper  and  tin,  but  not  of  cast 
metal  of  any  kind.  The  upright  support  can  be  of  brass,  and 
the  dishes  and  suspension  frames  of  platinum. 

The  sensibility  of  the  balance  increases  with  the  length  of 
the  arms,  which  should,  however,  have  a  certain  limit,  and  be 
as  nearly  uniform  as  possible  in  every  respect.  When,  through 
unskillful  construction,  the  length  of  one  arm  is  slightly 
greater  than  that  of  the  other,  in  order  to  avoid  the  error  in 
weighing  which  this  defect  would  occasion,  the  body  to  be 
weighed  is  placed  in  one  pan,  and  counter-balanced  by  weights 
in  the  other.  The  amount  of  weight  required  to  restore  the 
equilibrium  after  the  withdrawal  of  the  substance  is  its  cor- 
rect weight. 

In  order  to  avoid  friction,  the  parts  of  contact  should  be 


86  THE  BALANCE — ITS  REQUISITE  CONDITIONS. 

as  few  as  possible,  and  the  knife  edges  must  be  made  of  highly 
polished,  hardened  steel,  and  the  beds  or  planes  upon  which 
they  rest,  of  agate  or  flint.  The  accuracy  of  the  balance  will 
depend  greatly  upon  the  skill  and  precision  with  which  these 
portions  and  the  beam  are  elaborated. 

A  good  balance,  with  1  to  2000  grains  upon  each  dish, 
should  be  sensitive  to  the  one  or  two-thousandth  of  a  grain. 

"  To  obtain  the  greatest  degree  of  uniform  precision,  it  is 
requisite  that  the  beam  should  be  lifted  from  a  state  of  rest, 
in  a  perfectly  level  position,  and  that  the  stirrups  should  be 
lifted,  simultaneously,  with  their  loads,  from  their  rests  or 
supports ;  also  that  the  oscillations  of  the  stirrups  should  be 
prevented  or  checked  at  the  earliest  moment;  and,  finally, 
that  the  whole  system  should  be  left  at  liberty  with  delicacy 
and  exactitute,  so  as  to  remain  in  equilibrium,  or  vibrate  as 
the  case  may  be." 

"  To  command  the  above  conditions,  the  beam  should  be 
supported  upon  cones,  at  each  extremity,  adjusted  level  with 
each  other,  from  which  it  is  lifted,  by  a  plane  (and  not  a  por- 
tion of  a  hollow  cylinder,  as  is  usual)  which  rises  under  its 
centre  knife  edge,  and  to  which  it  is  returned  by  its  depres- 
sion, the  cones  guiding  the  beam  to  the  same  position  exactly 
from  which  it  was  elevated. 

"  The  stirrups,  in  like  manner,  should  hang  upon  hollow 
cones  or  V's,  so  as  to  be  taken  up  from,  and  returned,  inva- 
riably, to  the  same  position. 

"  The  beam  should  rest  upon  its  cones,  and  the  stirrups 
should  be  supported  by  their  V's  at  such  heights  as  to  relieve 
entirely  the  knife-edges,  with  a  sufficient  space  between  them 
and  their  respective  planes  to  permit  inspection  and  wiping, 
when  it  may  be  needed.  This  construction  admits  of  the 
placing  of  the  weights,  &c.,  and  guards  the  knife-edges  from 
the  consequences  of  displacement  during  use. 

"  The  beam  should  be  raised  by  the  elevation  of  the  centre 
plane,  subsequently  lifting  with  it  the  stirrups  with  their 
weights  and  load,  and  all  oscillation  checked  by  platforms 
placed  in  the  table  under  the  centre  of  the  stirrups,  which 
should  be  made  to  rise  simultaneously,  and  should  be  counter- 
weighed to  the  requisite  delicacy. 

"  The  descent  of  these  platforms,  effected  by  the  pressure 
of  a  finger  on  a  lever  conveniently  placed,  will  leave  the 
stirrups,  &c.,  at  liberty  to  vibrate,  or  bring  the  beam  to  a 


THE  MINT  BALANCE. 


87 


horizontal  position,  at  the  will  of  the  operator;  being  a  con- 
venient, certain,  and  rapid  method  of  manipulating,  not 
equaled  by  any  other  arrangement,  and,  in  fact,  essential  to 
a  well-constructed  balance." 

These  essential  qualities  of  an  accurate  balance  for  the 
more  delicate  operations  of  the  laboratory  are  comprised  in 
that  form  of  balance  used  in  the  United  States  Mint,  and 
which  "  combines  all  the  important  advantages  heretofore 
known  with  such  improvements  as  have  been  the  growth  of 
their  own  experience."  The  possession  of  one  of  these  in- 
struments does  away  with  the  necessity  of  a  separate  balance, 
exclusively,  for  dry  assays. 

Pig.  47  gives  a  front  view  of  this  balance.     We  take  our 

Fig.  47. 


description  from  the  Journal  of  the  Franklin  Institute,  vol. 


XIV. 


Description. — A  table,  marked  A,  is  furnished  with  level- 
ing screws  upon  the  front  and  back  edge,  and  at  each  end, 
marked  h.  In  Fig.  49,  which  exhibits  different  views  of  all  the 
parts,  the  leveling  screws  are  marked  5,  and  their  positions  in 
the  table  (the  view  of  the  under  side  of  which  is  given)  are 
marked  c. 

The  balance  is  intended  to  be  placed  upon  a  counter,  or  any 
other  firm  support,  and  the  table  leveled  by  means  of  the 
screws  last  described,  its  true  position  being  indicated  by  a 
plumb-line  and  weight  occupying  the  rear  opening  in  the 


88 


THE  MINT  BALANCE. 


column  (Fig.  49,  C) ;  the  plumb-line  and  weight  being  mark- 
ed d. 

The  column,  marked  C,  Figs.  47,  49,  contains  the  lifting 
apparatus,  and  supports  the  cap-plate,  marked  D.  The  cap- 
plate  guides  the  lifting  apparatus,  and  supports  the  V's,  or 
hollow  cones,  for  the  stirrups,  and  is  strengthened  and  stayed 
by  braces,  marked  E ;  the  section  of  which  braces  is  cruciform, 
with  circular  ends,  for  firm  bearing  upon  the  plate  and  base 
of  the  column,  to  which  they  are  secured  by  screws. 

Figs.  48,  49,  exhibit  upper  and  under  views  of  the  table, 
column,  plate,  &c.,  also  upper  and  lower  end  views  of  the 
column,  showing  the  means  of  its  attachment  to  the  table  and 
cap-plate. 


d^\ 


3 


The  lifting  apparatus  consists  of  a  winch-handle,  marked 
/,  Fig.  49,  fitting  upon  a  round  shaft,  g,  with  a  feather,  so  as  to 
admit  of  its  convenient  removal ;  upon  this  shaft  is  fitted  a  cam, 
A,  also  secured  by  a  feather  ;  the  cam  is  carefully  constructed, 
so  as  to  give  equal  elevation  to  equal  parts  of  its  revolution ; 
and  upon  the  cam  rests  a  roller,  ^,  which  turns  upon  a  pin  in 
the  frame,  /,  intended  to  reduce  friction,  and  give  facility  in 
raising  the  beam  with  its  load. 

The  lifting  frame,  /,  is  forked  cross-wise,  so  as  to  straddle 
the  shaft  and  accommodate  the  cam  and  roller,  at  the  same 
time  that  it  allows  the  necessary  vertical  motion,  without  the 
possibility  of  being  displaced;  all  of  which  is  exhibited  in  the 
two  views  of  the  lifting  frame  marked  y,  which  is  also  accom- 


THE  MINT  BALANCE.  89 

panied  by  sections  in  proximity  to  the  parts  which  they  are 
intended  to  explain. 

The  handle  is  so  placed  as  to  be  on  the  left  when  the  beam 
is  down  and  at  rest,  and  to  the  right  when  the  beam  is  raised, 
in  the  act  of  weighing,  and  makes,  together  with  the  cam, 
more  than  three-fourths  of  a  revolution,  the  cam  having  a  very 
slight  depression  upon  its  upper,  or  highest  point,  into  which 
the  roller  falls,  maintaining  it  in  its  position  when  the  beam 
is  raised.  It  is  then  extended  beyond  the  centre  of  the 
roller,  so  as  to  be  stopped  at  the  limit  of  motion,  as  exhibited 
h,  Fig.  49. 

Fig.  49. 


The  lifting  frame  is  forked  at  the  top  for  the  accommoda- 
tion of  the  beam.  Upon  it  rests  the  plane,  the  top  and  side 
view  of  which  are  marked  A?,  for  the  support  of  the  centre 
knife-edge,  secured  to  the  frame  by  screws.  In  balances  of 
ordinary  construction,  this  plane  may  be  made  of  hardened 
cast-steel;  in  finer  instruments,  of  bronze,  or  brass,  with  an 
inserted  block  of  polished  agate,  secured  by  fusible  metal,  or 
cement. 

The  position  of  the  handle,  lifting  frame,  &c.,  are  exhibited 
with  sufficient  clearness  in  the  front  view.  Fig.  47. 

The  cap-plate,  views  of  the  upper  and  under  sides  of  which 
are  given  at  D,  Fig.  48,  is  constructed  with  horizontal  spaces 
at  the  centre  and  each  end.  In  the  middle  it  is  secured  to  the 
column  by  four  screws,  and  to  the  braces  B  in  the  same  man- 
ner, the  holes  for  which  are  marked  in  all  the  views. 

The  square  opening  in  the  middle  serves  as  a  guide  and 
7 


90  THE  MINT  BALANCE. 

support  to  the  lifting  frame,  which  must  be  accurately  fitted, 
so  as  to  prevent  any  lateral  play. 

The  horizontal  spaces  at  the  extremity  of  the  cap-plate 
support  short  pillars  terminated  by  cones,  upon  which  the 
beam  rests;  these  pillars  are  secured  to  the  cap-plate  by 
screws  passing  through  it  from  the  under  side,  the  holes 
through  which  they  pass  being  large  enough  to  admit  of  the 
adjustment  of  the  beam  to  its  proper  place,  previous  to  their 
being  permanently  fastened  down. 

The  details  of  these  pillars  are  given  at  Z,  Fig.  49,  the  cones 
being  constructed  of  cast  steel,  hardened  and  polished. 

The  same  space  also  supports  the  V's,  or  guide  supports  of 
the  hangers,  difiPerent  explanatory  views  of  which  are  given  in 
Fig.  49,  the  V's  being  marked  w,  and  the  hangers  n.  All 
these  parts  have  been  devised  with  reference  to  the  simplest 
and  most  economical  construction  consistent  with  the  requisite 
accuracy,  and  for  affording  the  greatest  facility  in  the  final 
adjustment  of  the  balance. 

The  most  important  part  of  the  balance  is  the  beam  o ; 
Fig.  49  exhibits  side  and  top  views.  The  projections  marked 
q,  are  the  supports  of  the  beam  when  at  rest ;  the  conical 
cavities,  indicated  by  dotted  lines,  being  made  to  fit  the  cones 
marked  I. 

This  form  of  beam  affords  facility  in  construction,  being 
composed  of  straight  surfaces,  without  ribs  or  curves;  is  well 
adapted  to  maintain  its  form  when  loaded;  affords  the  least 
surface  for  accumulation  of  dust,  and  is  readily  wiped  when  it 
may  be  necessary.  The  means  of  adjustment  for  the  length 
of  arm  is  exhibited  at  r.  Fig.  49. 

It  will  be  seen,  that  the  needle  of  the  balance,  which  is  the 
subject  of  description,  is  pointed  downwards,  and  there  are 
good  reasons  for  this  disposition.  In  the  first  place  it  is 
directly  before  the  eye  of  the  operator,  and,  therefore,  more 
convenient  in  use,  than  it  is,  when  elevated  above ;  again  it 
may  be  made  longer  than  the  arms  of  the  beam,  and  will, 
consequently,  describe  a  larger  arc,  and  thus  give  more  dis- 
tinct indications,  whilst  the  whole  arrangement  need  occupy 
no  more  space  than  is  requisite  for  the  other  parts ;  and, 
finally,  the  needle  is  protected  from  external  injury  by  the 
lifting-frame  and  column,  in  the  centre  of  which  it  is  placed. 

The  parts  which  remain  to  be  described  have  been  usually 
considered  of  minor  importance,  but  experience  has  shown 


THE  MINT  BALANCE.  91 

that  this  estimate  is  scarcely  a  just  one,  inasmuch  as  they 
afford  facilities  for  accuracy  and  rapidity,  that  leave  no  doubt 
of  their  value,  and  place  them  in  a  most  important  position 
in  practice.  The  parts  now  alluded  to,  constitute  the  system 
by  which  the  operator  is  enabled  to  find  the  equilibrium  of 
which  he  is  in  search.  It  consists  of  the  pedestals,  as  they 
have  been  termed,  marked  s,  Figs.  47  and  48,  and  the  parts 
connected  with  them,  marked  t,  u,  v  and  w,  in  Fig.  48;  a 
light  shaft,  made  of  tubular  iron,  ^,  supported  by  pivots  u^ 
which  pivots  are  screwed  through  a  piece  cast  on  the  under 
side  of  the  table,  marked  V ;  upon  the  ends  of  this  shaft  there 
are  levers,  W,  upon  the  ends  of  which  levers,  when  in  place, 
the  pedestals  rest. 

The  remaining  part  of  this  system  is  a  double  armed  lever, 
placed  in  the  middle  of  the  shaft,  ^,  (represented  in  the  en- 
graving detached,)  and  marked  x',  it  is  connected  by  a  pin, 
with  the  trigger,  ^,  represented  in  its  place  in  Fig.  48,  with 
the  same  letter.  Upon  the  other  end  of  the  lever,  a:,  there  is 
a  weight,  y,  capable  of  adjustment  by  a  screw  upon  which  it 
traverses,  so  that  it  may  be  made  to  approach,  or  recede  from 
the  shaft,  t. 

The  action  of  this  system  is  easily  understood ;  its  whole 
object  is  to  depress  the  platforms  by  sufficient  force,  applied 
by  the  finger,  to  the  trigger,  the  counter  weight  returning 
them  to  their  original  position,  after  its  removal. 

It  will  be  seen,  by  reference  to  Fig.  47,  that  the  under 
sides  of  the  stirrups  have  a  space,  represented  by  dotted  lines, 
in  which  the  platforms  are  placed,  which  allows  the  stirrups 
to  oscillate  within  its  limits,  but  beyond  which  they  cannot 
move.  This  construction  is  intended  to  guard  the  hangers 
from  displacement,  and  to  prevent  injury  by  too  much  move- 
ment of  the  stirrups,  an  accident  very  likely  to  occur,  when 
the  pans  or  weights  are  hastily  removed,  especially  in  the  use 
of  heavy  weights  or  large  masses. 

The  cavity,  whose  object  was  described  in  the  last  para- 
graph, forming  the  under  side  of  the  base  of  the  stirrups,  is 
turned  as  truly  as  possible  in  the  form  of  a  portion  of  a  sphere, 
whose  radius  is  its  distance  from  the  bearing  of  the  knife-edge. 
The  platforms  are  adjusted  by  means  of  the  counter  weight, 
so  as  to  press  lightly  up  against  the  stirrups,  and  to  follow 
them  when  raised. 

It  is  found  convenient  in  practice  to  turn  the  handle  of  the 


92  THE  MINT  BALANCE — ITS  SUPERIOKITY. 

balance  but  a  small  portion  of  its  movement,  if  the  weights 
are  not  equal  on  opposite  sides,  a  circumstance  to  be  expected 
when  searching  for  a  weight.  The  heavy  side  will  remain 
down,  and  the  needle  will  indicate  whether  addition  of  weight, 
or  its  removal  is  requisite.  These  trials  are  continued  until 
the  platforms  follow  up  the  whole  lift,  the  needle  remaining 
opposite  the  middle  line  of  its  scale,  until  the  handle  is  stopped 
by  its  limit  of  motion,  where  it  remains.  The  finger,  then, 
by  pushing  down  the  trigger,  will  depress  the  platforms,  when 
smaller  weights  are  employed  until  the  needle  indicates  equi- 
librium. 

In  this  balance  there  is  little  or  no  embarrassment  from 
oscillation,  because  the  stirrups  immediately  accommodate 
themselves  to  the  position  of  the  weights,  the  light  pressure 
permitting  them  to  take  any  position  required  by  the  load ; 
nevertheless,  having  sufficient  power,  from  their  pressure,  to 
prevent  any  swinging.  If  from  any  cause  the  stirrups  should 
be  in  motion,  three  consecutive  depressions  of  the  platforms, 
will  bring  them  to  a  state  of  rest,  with  absolute  certainty,  and 
with  a  loss  of  time  so  short  as  to  be  entirely  immaterial. 

The  stirrups  are  connected  with  the  hangers,  by  a  rod, 
which  is  double-jointed,  as  near  to  the  hangers  as  possible,  so 
as  to  allow  perfect  freedom  of  motion ;  at  the  same  time,  so 
well  fitted  as  to  allow  no  change  of  position  in  the  parts.  On 
the  lower  ends  of  these  rods,  there  are  screws  and  nuts,  to 
regulate  the  height  of  the  stirrups,  together  with  a  jam  nut, 
to  prevent  any  change  after  the  adjustment  has  been  satis- 
factorily made. 

The  bases  of  the  stirrups  are  designedly  made  small,  re- 
quiring the  use  of  a  dish  on  the  one  side,  and  a  platform  for 
weights  on  the  other.  This  dish  and  platform  being  made  of 
equal  weight,  renders  the  use  of  a  counter  weight  unnecessary, 
and  as  the  balance  cannot  be  used  without  both,  the  liability 
to  mistakes  from  this  cause  is  entirely  avoided. 

Kater's  and  Robinson's  balance,  which,  though  more  compli- 
cated, and  less  preferable  for  other  reasons  to  the  preceding, 
is  the  most  popular  balance  for  estimating  minute  quantities 
with  precision ;  and,  indeed,  for  all  the  weighing  operations  of 
delicate  research.  When  carefully  preserved,  it  retains  its 
sensibility  for  many  years.  Fig.  50  represents  one  made  by 
Mr.  J.  P.  Duffey,  of  Philadelphia,  who  has  acquired  great 
skill  and  accuracy  in  the  construction  of  fine  balances.     An 


eater's  and  ROBINSON'S  BALANCE. 
Fig.  50. 


93 


improvement  which  he  has  added  to  those  of  recent  manufac- 
ture, is  both  simple  and  useful.  It  consists  of  an  elastic 
spring,  A  A,  Fig.  51,  serv- 
ing as  a  support  for  the 
dishes  when  the  balance  is  at 
rest ;  and  at  the  same  time 
so  arranged,  that  by  the 
depression  of  the  thumb 
lever  suitably  attached,  the 
dishes  are  thrown  off  their 
supports,  and  the  beam  put  into  action  simultaneously.  We 
are  indebted  for  our  description  to  Lardners  Elements  of 
Mechanics. 

"  The  beam  of  this  balance  is  only  ten  inches  long.  It  is 
a  frame  of  bell-metal  in  the  form  of  a  rhombus.  The  ful- 
crum is  an  equilateral  triangular  prism  of  steel,  one  inch  in 
length;  but  the  edge  on  which  the  beam  vibrates  is  formed  to 
an  angle  of  120°,  in  order  to  prevent  any  injury  from  the 
weight  with  which  it  may  be  loaded.  The  chief  peculiarity 
in  this  balance  consists  in  the  knife-edge,  which  forms  the 


94  ROBINSON'S  BALANCE. 

fulcrum,  bearing  upon  an  agate  plane  throughout  its  whole 
length;  whereas  in  the  other  balances  the  whole  weight  is 
supported  by  portions  only  of  the  knife-edge,  amounting 
together  to  one-tenth  of  an  inch.  The  supports  for  the  scales 
are  knife-edges,  each  six-tenths  of  an  inch  long.  These  are 
each  furnished  with  two  pressing  screws,  by  means  of  which 
they  may  be  made  parallel  to  the  central  knife-edge. 

"Each  end  of  the  beam  is  sprung  obliquely  upwards  and 
towards  the  middle,  so  as  to  form  a  spring  through  which  a 
pushing  screw  passes,  which  serves  to  vary  the  distance  of 
the  point  of  suspension  from  the  fulcrum,  and,  at  the  same 
time,  by  its  oblique  action,  to  raise  or  depress  it,  so  as  to  fur- 
nish a  means  of  bringing  the  points  of  suspension  and  the 
fulcrum  into  a  right  line. 

"  A  piece  of  wire,  four  inches  long,  on  which  a  screw  is  cut, 
proceeds  from  the  middle  of  the  beam  downwards.  This  is 
pointed  to  serve  as  an  index,  and  a  small  brass  ball  moves  on 
the  screw,  by  changing  the  situation  of  which  the  place  of  the 
centre  of  gravity  may  be  varied  at  pleasure. 

"  The  fulcrum,  as  before  remarked,  rests  upon  an  agate 
plane  throughout  its  whole  length,  and  the  scale-pans  are 
attached  to  planes  of  agate,  which  rest  upon  the  knife-edges, 
forming  the  points  of  support.  This  method  of  supporting 
the  scale-pans,  we  have  reason  to  believe,  is  due  to  Mr. 
Cavendish.  Upon  the  lower  half  of  the  pillar,  to  which  the 
agate  plane  is  fixed,  a  tube  slides  up  and  down  by  means  of 
a  lever  which  passes  to  the  outside  of  the  case.  From  the 
top  of  this  tube,  arms  proceed  obliquely  towards  the  ends  of  the 
balance,  serving  to  support  a  horizontal  piece,  carrying  at 
each  extremity  two  sets  of  Ys,  one  a  little  above  the  other. 
The  upper  Y  s  are  destined  to  receive  the  agate  planes  to 
which  the  scale-pans  are  attached,  and  thus  to  relieve  the 
knife-edges  from  their  pressure ;  the  lower  to  receive  the 
knife-edges  themselves,  which  form  the  points  of  suspension 
of  the  pans,  consequently  these  latter  Ys,  when  in  action, 
sustain  the  whole  beam. 

"  When  the  lever  is  freed  from  a  notch  in  which  it  is  lodged, 
a  spring  is  allowed  to  act  upon  the  tube  we  have  mentioned, 
and  to  elevate  it.  The  upper  Ys  first  meet  the  agate  planes 
carrying  the  scale-pans,  and  free  them  from  the  knife-edges. 
The  lower  Ys  then  come  into  action  and  raise  the  whole 
beam,  elevating  the  central  knife-edge  above  the  agate  plane. 


BERLIN  BALANCE. — TRALLE'S  BEAM. 


95 


This  is  the  usual  state  of  the  balance  when  not  in  use :  when 
it  is  to  be  brought  into  action,  the  reverse  of  what  we  have 
described  takes  place.  On  pressing  down  the  lever,  the  cen- 
tral knife-edge  first  meets  the  agate  plane,  and  afterwards 
the  two  agate  planes,  carrying  the  scale-pans,  are  deposited 
upon  their  supporting  knife-edges. 

"  A  balance  of  this  construction  was  employed  by  Captain 
Kater,  in  adjusting  the  national  standard  pound.  With  a 
pound  troy  in  each  scale,  the  addition  of  one-hundreth  of  a 
grain  caused  the  index  to  vary  one  division,  equal  to  one- 
tenth  of  an  inch;  and  Mr.  Robinson  adjusts  these  balances 
so  that  with  one  thousand  grains  in  each  scale,  the  index 
varies  perceptibly  on  the  addition  of  one-thousandth  of  a  grain, 
or  of  one-millionth  part  of  the  weight  to  be  determined." 

A  balance  of  this  or  the  preceding  kind,  necessarily  costly 
($85  to  $100)  from  the  great  care  required  in  its  construc- 
tion, is  only  needed  for  the  weighing  of  minute  quantities  of 
matter  in  scientific  researches,  and  where  it  is  desirable  to 
estimate  the  least  appreciable  difierences  of  weight.  An  in- 
strument well  calculated  for  all  the  ordinary  purposes  of 
analysis,  is  the  Berlin  balance.  Fig.  52. 
Those  manufactured  by  E.  N.  Kent,  New 
York,  are  guaranteed,  when  loaded  with 
50  grammes  in  each  pan,  to  turn  with 
•005  grammes,  or  yu-ooo*^  P^^*  ^^  *^® 
weight.  Its  cost,  with  an  extra  pan  for 
taking  the  specific  gravity  of  bodies,  and 
glass  case,  containing  a  drawer  with  divi- 
sions to  receive  the  different  parts  of  the 
balance,  and  thus  render  it  portable,  is 
thirty  dollars. 

In  many  processes,  and,  indeed,  in  some  few  instances  of 
analysis,  for  example  of  gold  ores  and  of  vegetable  matters,  one 
or  more  constituents  of  which  are  only  obtainable,  even  in 
minute  quantities,  from  large  amounts  of  the  material,  it  is 
necessary  to  have  a  second  balance  calculated  to  weigh  from  a 
quarter  of  an  ounce  to  five  pounds  with  such  precision  that 
one  or  two  grains  will  turn  the  dish  when  loaded  with  its 
greatest  weight.  Fig.  53  represents  a  balance  of  this  kind, 
made  after  a  Tralles  beam,  by  DufFey,  of  this  city.  It  con- 
sists of  two  brass  dishes,  A  A,  suspended  by  loops,  D  D, 
which  rest  upon  the  steel  knife-edges  at  the  extremities  of  the 


Fig.  52. 


/          \ 

aI/ 

1 

/kiJ      t^       id 

^ 

I °- — ^ 

96 


PRESERVATION  OF  THE  BALANCE. 


beam  C.  The  beam  is  supported  by  the  knife-edge  in  its 
centre  as  at  E,  and  the  whole  balance  is  suspended  to  an  up- 
right, crooked  at  its  top,  by  the  hanger  B.  Annexed  to  the 
centre  of  the  beam  is  a  long  vertical  needle,  which,  following 
the  vibrations  of  the  beam,  serves  to  indicate  the  least  oscil- 
lation, which  is  rendered  more  perceptible  by  an  ivory  seg- 

Fig.  53. 


ment  situated  behind  its  point,  and  divided  into  degrees. 
This  balance  is  placed  in  the  room  D,  PI.  2,  upon  the  table 
adjoining  that  upon  which  is  the  finer  balance.  The  support 
to  which  it  is  suspended  may  be  either  of  wood  or  metal.  To 
prevent  damage  to  the  knife-edges,  the  dishes,  when  the 
scales  are  not  in  use,  should  be  unhung,  and  the  whole  balance 
kept  covered  with  a  linen  cover,  distended  over  a  wire  frame 
work,  which  may  be  suspended  by  a  cord  upon  a  pulley,  and 
counterpoised  so  as  to  admit  of  being  readily  raised  or  lowered. 
Preservation  of  the  Balances. — Each  of  the  finer  balances 
should  have  a  separate  table,  and  these  tables  a  permanent 
position  in  a  close,  well-lighted  room,  expressly  appropriated 
for  the  purpose.  The  top  of  the  table  must  be  of  hard  wood 
and  perfectly  horizontal ;  and  to  secure  the  table  itself 
against  the  slightest  jarring  motion,  it  may  be  tightly  fastened 
to  the  floor  by  iron  clamps  and  screws  fitted  to  its  legs.    Great 


PRESERVATION  OP  THE  BALANCE.  97 

care  is  requisite  to  have  it  plumb.  Of  the  two  drawers  which 
it  should  contain,  one  is  for  the  spatulas,  spoons,  crucible 
tongs,  papers,  watch  glasses,  and  other  implements  used  in 
weighing ;  the  other  may  be  fitted  deskwise,  and  furnished 
with  slips  of  paper,  or  a  porcelain  slate  and  pencil,  to  aflFord 
convenience  in  recording  the  weights.  A  polished  cast-iron 
slab  about  six  inches  square,  upon  which  to  set  the  heated 
crucibles  and  promote  their  cooling  by  conducting  off  the 
excess  of  heat  previous  to  weighing,  may  be  considered  a 
necessary  accompaniment  to  the  table.  In  order  to  preserve 
its  brightness,  it  should  be  encased  in  a  woolen  bag  and  kept 
within  the  drawer  when  not  in  use ;  or  it  may  be  enclosed  in 
a  frame  with  a  sliding  cover,  and  fastened  to  the  top  of  the 
table  near  to  one  of  its  corners.  The  cover  which  protects  its 
surface  from  oxidation  can  readily  be  drawn  out  whenever  it 
is  required  to  use  the  slab. 

It  is  not  sufficient  for  the  preservation  of  the  delicacy  of 
the  balances,  that  the  room  in  which  they  are  kept  should  be 
dry  and  tight.  Vapors,  aqueous  and  corrosive,  will  in  divers 
ways  find  entrance  into  the  apartment,  and  so,  therefore,  be- 
sides the  precaution  of  lacquering  the  brass  and  steel  parts  of 
the  balance,  the  instrument  should  be  enclosed  in  a  sufficiently 
capacious  mahogany  or  walnut  case,  with  sash  doors  in  the 
front  and  back,  and  sash  windows  at  either  side.  The  doors 
should  be  always  kept  closed  and  fastened  by  their  buttons 
when  the  balance  is  not  in  use,  else  the  entrance  of  dust  and 
moisture  will  impair  its  accuracy.  An  additional  and  very 
efiectual  precaution  against  oxidation  by  moisture,  is  to  keep 
constantly  within  the  case  a  capsule  containing  some  ab- 
so'rbent  matter,  as  fused  chloride  of  calcium  or  carbonate  of 
potassa.  By  an  occasional  renewal  of  the  absorbent  matter, 
the  atmosphere  within  the  case  can  be  kept  very  dry.  The 
multiplication  of  door- ways  is  to  afford  facility  for  the  passage 
and  weighing  of  long  tubes,  which  have  to  be  placed  across 
the  pan.  The  divisions  in  the  drawer  at  the  bottom  of  the 
case  must  be  lined  with  velvet,  and  so  arranged  as  to  receive 
the  different  parts  of  the  balance,  and  allow  its  transportation 
without  the  least  risk  of  damage. 

In  order  to  preserve  the  edges  of  the  knives,  the  beam 
should  always  be  thrown  out  of  action  when  the  balance  is 
not  in  use,  otherwise  their  constant  contact  with  the  planes 
and  the  pressure  of  the  balances,  as  well  as  the  sudden 


98  THE  BALANCE — THE  WEIGHTS. 

addition  of  a  heavy  weight,  will  injure  their  delicacy. 
Duffy's  support,  with  its  thumb  lever  outside,  before  men- 
tioned, affords  a  means  of  not  only  preventing  these  contin- 
gencies, but  also  of  communicating  motion  to  the  beam,  without 
the  necessity  of  opening  the  doors,  and  consequent  exposure 
of  the  balance. 

The  three  or  four  feet  upon  which  the  case  rests  have  screws 
passing  through  them.  These  serve  to  give  the  balance  a  per- 
fectly horizontal  position,  even  upon  an  uneven  surface — the 
level  being  obtained  by  raising  or  depressing  either  of  the 
screws,  as  the  case  requires,  and  as  will  be  indicated  by  the 
two  spirit  levels  which  should  be  fitted  to  the  pedestal  of  each 
balance. 

The  position  of  the  balance  should  be  with  due  regard  to 
light,  but  while  placed  near  the  window,  to  afford  facility  in 
perceiving  the  slightest  oscillations  of  the  needle,  it  should  be 
free  from  any  sudden  actions  of  the  solar  rays,  which,  by  pro- 
ducing unequal  expansion  of  the  different  parts  would  occasion 
inexact  results  in  weighing. 

The  balances  should  be  cleansed  and  adjusted  whenever 
they  have  become  inaccurate,  for  it  is  almost  impossible  for 
even  the  best  balance  to  retain  its  sensitiveness  indefinitely. 
This  work  should  rather  be  confided  to  a  manufacturer  of 
balances,  as  it  requires  both  skill  and  experience.  Slight 
discrepancies  in  the  weight  of  the  two  dishes  can  be  tempo- 
rarily compensated  for  by  adding  to  that  dish  which  is  defi- 
cient, sufficient  weight  to  restore  its  equilibrium. 


CHAPTER    VI. 

THE  WEIGHTS. 

There  are  three  sets  of  weights  requisite,  of  which,  one  for 
the  common  scales  of  the  operating  room  should  be  avoirdu- 
pois, and  range  from  eight  or  more  pounds  downward  to  an 
ounce  or  less.  These  weights  are  for  the  rougher  operations 
of  weighing,  and  may  be  of  cast  iron,  with  a  coating  of  black 
japan  to  protect  them  against  oxidation. 


THE  BALANCE — THE  WEIGHTS.  99 

For  the  second  balance  (Fig.  52)  the  weights  must  be  of 
brass,  in  the  form  of  short  cylinders/,  Fig.  56,  with  knobs  at  the 
top,  and  should  range  from  25,000  to  10  grains,  decreasing  by 
fives,  in  the  series  to  500,  as  follows:  25,000,  20,000, 15,000, 
10,000,  5000,  1000,  500;  and  from  that  point  in  ratio  as  fol- 
lows: 400,  300,  200,  100,  50,  30,  20, 10,  so  as  to  make  alto- 
gether 15  weights;  the  whole  to  be  enclosed  in  a  suitable  box 
with  a  hinged  cover. 

These  latter  weights,  though  required  to  be  accurately  ad- 
justed, are  not  necessarily  so  nicely  precise  as  those  for  the 
analytic  balances  (Figs.  47,  50).  They  should  always  be  sub- 
divided after  the  decimal  system,  so  that  ten  of  the  smaller 
weights  will  make  one  of  the  next  highest  class.  This  arrange- 
ment (so  that  they  perfectly  agree  with  each  other  of  the  same 
denomination)  will  render  it  unimportant  whether  they  be  grain 
or  French  gramme  weights,  the  two  kinds  almost  exclusively 
used  in  scientific  research. 

If  they  are  grain  weights,  the  series  should  range  from 
5000  grains  to  jo^oo*^  ^^  ^  grain,  as  follows: — 5000,  3000, 
2000,  1000,  500,  300,  200,  100,  50,  30,  20,  10,  5,  3,  2,  1, 
.1,  .2,  .3,  .5,  .05,  .03,  .02,  .01,  .005,  .003,  .002.  The  gramme 
weights  range  from  one  centigramme  to  one  milligramme. 
The  divisions  of  the  gramme  (the  standard  unit  of  the  French 
weights)  are  the  decigramme  =  j^^th  gramme;  the  centigramme 
=  y J^th  gramme;  the  milligramme  =  j^QQth  gramme.  Its 
multiples  are  the  decagramme  =  10;  the  hectogramme  =i  100; 
the  kilogramme  =  1000 ;  and  the  mp^iagramme  =  10,000 
grammes.  The  table  below  shows  the  relative  value  and  pro- 
portions of  the  French  decimal  and  troy  and  avoirdupois 
weights. 

Metrical  or  Decimal  Weights. 


Equiv.  in  Troy 

Equiv.  in  avoirdupois 

Names. 

Equlv.  in  grammes. 

grains. 

weight. 

lbs.    oz.      grs.  ■■    '  • 

Milligramme 

.001 

.0154 

', 

Centigramme 

.01 

.1543 

Decigramme 

.1 

1.5434 

/ 

Gramme 

1. 

•      15.434 

^     '• 

Decagramme 

10. 

154.3402    , 

.    ■.•      Oi     45w  o  .  • 

Hectogramme 

100. 

1543.4023  , 

3^.!  2.1^2 

Kilogramme,  or 

Kilo 

1000. 

15434.02:>4     ^ 

2     3}     l,2;r73 

Myriagramme 

10000. 

154340.2344 

22     0|    u2. 

All  of  the  weights  for  the  fine  Oalance  must  be  adjusted 


100  THE  BALANCE — THE  WEIGHTS. 

with  the  nicest  accuracy,  and  before  being  used  should  be 
compared  with  others  of  attested  correctness.  Of  the  French 
weights  those  from  the  milligramme  to  the  gramme  should  be 
of  platinum;  and  so,  also,  of  the  grain  weights,  those  from  the 
ten  grain  weight  downwards  should  be  of  the  same  metal. 
Palladium  being  of  but  half  the  specific  gravity  of  platinum, 
and  similar  to  it  in  other  respects,  is  sometimes  used  for  the 
fractional  grain  weights,  because  of  the  greater  relative  sur- 
face which  it  presents.  The  remaining  larger  weights,  to  save 
expense,  may  be  of  brass,  and,  to  preserve  them  from  oxida- 
tion, should  either  be  covered  with  a  thin  coat  of  lacquer  or 
else  galvanized  with  gold  or  platinum. 

Each  set  should  contain  duplicates  of  the  10,  2  and  1  grain 
weights;  triplicates  of  the  .2,  .1,  .02,  .01,  and  quadruplicates  of 
the  .001  grain  weights;  in  many  instances,  especially  in  taking 
specific  gravities,  these  additional  weights  are  indispensable. 

In  order  to  preserve  the  weights  free  from  dust  and  oxida- 
tion, they  must  be  encased  in  a  close  box  with  hinged  cover 
and  fastenings.  The  interior  of  the  box  is  divided  into  com- 
partments, lined  with  velvet  to  prevent  abrasion  of  the  sur- 
faces of  the  weights,  each  of  which  should  have  a  separate 
division.  The  edges  of  every  compartment  should  be  marked 
in  ink  with  the  value  of  the  weight  it  contains ;  and  the  weights 
themselves  must  have  their  denominations  stamped  upon  them. 
The  series  must  be  so  accurately  adjusted,  that  the  difference 
between  any  one  of  the  large  weights  and  the  combined  num- 
ber of  smaller  ones,  equal  to  it,  shall  not  be  perceptible  in  a 
balance  turning  with  one-tenth  of  a  milligramme. 

To  test  their  accuracy,  take  any  two  of  them  of  the  same 
denomination,  convey  them,  with  the  fork  or  forceps,  to  the 
balance,  and  place  one  in  each  dish.  If  the  beam  upon  being 
put  in  action  is  in  perfect  equilibrium,  the  weights  are  uni- 
form, and  can  serve  as  standards.  Now,  for  further  verifica- 
tion, place  both  together  in  one  dish,  and  in  the  opposite  pan 
add  enough  of  smaller  weights  to  equal  that  of  the  two  com- 
bined. If  the  beam  still  retains  its  equilibrium,  when  put  in 
action,  the  weights  may  be  considered  correct. 
'"As  Treqiient' /'handling  of  the  weights  with  the  fingers 
wouM*  ta.rnish  th^m]  and  otherwise  injure  their  value,  a  small 
fork  and"  ?.'pair  of  fr»rc6ps  are  necessary  accompaniments  to 
each  set  of  weights.  "  The,  fork,  represented  by  Fig.  54,  made 
of  either  ivory,  horn  or  wood,und  being  intended  for  raising 


THE  BALANCE — THE  WEIGHTS. 


101 


the  brass  weights,  has  its  notches  at  either  end  of  different  size, 
so  as  equally  to  accommodate  the  knobs  of 
both  the  larger  and  smaller  weights.  A  Fig-  ^4.  Fig.  55. 
small  pair  of  elastic  forceps,  Fig.  55,  of 
brass  or  plated,  or  polished  steel,  with 
platinum,  or  ivory  points,  serve  for  the 
smaller  platinum  weights,  which,  for  con- 
venience of  handling,  should  be  turned  up 
at  one  corner,  as  at  g,  Fig.  56. 

The  box  should  be  closed  after  each 
weighing,  and,  to  preserve  it  from  the  cor- 
rosive vapor  that  may  be  floating  about, 
should  be  kept  in  the  drawer  of  the  balance  table. 

Fig.  56,  represents  a  box  of  weights  and  all  the  necessary 

Fig.  56. 


'?^ 


^ 


appurtenances.  The  ribs  a  a  a,  fitted  to  the  interior  of  the 
top,  by  pressing  against  them  when  the  box  is  closed,  keep 
the  weights  in  their  places.  The  fork  and  forceps  are  shown 
in  place  at  b  h.  The  channel  d,  kept  always  covered  with  a 
thick  glass  plate,  contains  the  platinum  weights,  an  extra 
quantity  of  the  smaller  of  which  are  kept  in  the  cavity  e. 
These  cases  and  the  weights,  accurately  adjusted  and  finely 
finished,  can  be  purchased  of  either  Kent  or  Duffey. 

Small  weights,  to  supply  the  place  of  such  as  may  be  acci- 
dentally lost,  can  be  made  by  first  determining  the  weight  of 
a  given  length  of  wire  of  uniform  thickness  throughout,  and 
then  dividing  it  into  perfectly  equal  parts ; — the  number  of 
the  divisions  indicates  the  fraction  of  the  original  weight  which 
they  represent  as  a  whole ;  for  instance,  if  the  wire  weighed 
ten  grains;  and  is  divided  into  10  or  20  portions,  each  frac- 
tion will  represent  a  grain  or  half  grain,  accordingly.     By 


102  THE  BALANCE — WEIGHING. 

using  wire  of  greater  thickness,  weights  of  augmented  value 
can,  in  like  manner,  be  made  and  adjusted. 

Shot,  of  which  there  should  be  a  box  of  the  several  sizes 
kept  in  the  balance  table-drawer,  are  convenient  counterpoises 
for  tubes,  capsules,  crucibles,  watch  glasses,  and  other  recepta- 
cles for  substances  to  be  weighed. 


CHAPTER    VII. 

WEIGHING. 

There  are  certain  preliminaries  to  be  observed  in  all  deli- 
cate weighing  operations,  of  which  the  most  important  is  to 
ascertain  whether  the  balance  is  in  order,  as  regards  equili- 
brium and  freedom  of  oscillation.  To  do  this,  each  dish  should 
be  loaded  nearly  to  the  full  extent  of  the  power  of  the  balance. 
If,  when  the  beam  is  put  in  action,  there  is  no  perceptible  va- 
riation in  the  dishes,  the  equilibrium  is  perfect.  For  further 
verification,  there  should  be  an  exchange  of  loads,  from  one 
dish  to  the  other,  and  the  beam  again  set  in  motion.  The 
recovery  of  the  equilibrium,  after  the  cessation  of  the  vibra- 
tions indicates  the  correctness  of  the  balance.  The  need  of 
more  than  a  milligramme  for  the  analytic  balance,  or  of  y'^th 
of  a  milligramme  in  the  more  delicate  balance,  to  restore  a 
deficiency  in  either  dish,  should  condemn  the  instruments  for 
quantitative  examinations,  unless  previously  adjusted.  This 
is  done  by  the  addition  of  bits  of  tin-foil  to  that  dish  which  is 
lightest.  When,  however,  the  balance  is  carefully  used,  and 
by  but  one  operator,  it  will  be  only  necessary  to  reassure  him- 
self of  its  equilibrium  in  those  weighings  where  absolute  accu- 
racy is  all  important.  Be  careful,  however,  in  adjusting,  as 
well  as  in  weighing,  that  the  weights  in  the  pan  do  not  over- 
load the  balance  and  make  it  set^  an  efi'ect  the  more  prompt, 
in  proportion  to  the  greater  accuracy  and  sensibility  of  the 
balance.  The  setting,  which  makes  one  scale  appear  heavier 
than  the  other,  is  a  permanent  depression  of  the  lowest  pan 
by  the  slightest  impulse  to  the  exactly  horizontal  beam  of  a 


THE  BALANCE — WEIGHING.  103 

surcharged  balance.  Hence  the  necessity  of  loading  the  ba- 
lance within  the  limit  of  its  maximum  power. 

In  all  weighing  operations,  the  counterpoising  of  substances 
is  more  speedily  attained,  and  with  less  injury  to  the  balance, 
by  systematically  following  a  weight,  which  is  removed  from 
the  pan  as  too  heavy,  by  the  next  in  succession,  until  equili- 
brium is  obtained.  Thus,  in  balancing  a  watch  glass,  if  the 
50  grain  weight  drags  the  beam,  replace  it  by  the  15 ;  if  this 
is  still  too  much,  use  the  10  weight ;  and  if  this  is  too  little, 
make  up  the  deficiency  with  the  smaller  weights,  added  con- 
secutively, and  decreasing  gradually  their  denomination  as  the 
counterpoise  is  approached. 

To  preserve  the  accuracy  of  the  balance,  it  should  be  put 
out  of  action  upon  every  addition,  removal,  or  substitution  of 
weights.  As  a  precaution  against  error,  the  weights  must 
always  be  removed  from  the  pan  and  spread  upon  white  paper 
to  be  counted;  and  to  verify  the  aggregate,  in  putting  them 
away,  their  denominations  should  also  be  compared  with  their 
value,  as  marked  upon  the  vacancies  which  they  occupy  in  the 
box  in  which  they  are  kept.  The  slips  of  paper  and  porce- 
lain slate,  in  the  table-drawer,  serve  to  make  notes  of  their 
amount,  which  should  be  done  before  placing  them  in  the  box. 

A  provision  against  inaccuracy,  from  very  slight  inequality 
of  the  arms  of  the  beam  or  imperfect  equilibrium  from  other 
causes,  is  the  invariable  use  of  the  same  pan  for  the  reception 
of  the  substance  to  be  weighed.  By  this  practice,  notwith- 
standing the  difference  in  the  weights  of  the  two  dishes,  the 
ratio  being  kept  uniform,  the  quantities  will  be  proportionably 
augmented  or  decreased,  so  that  the  products  of  analyses  can 
be  as  accurately  estimated  as  in  a  perfect  balance.  An  alter- 
nate use  of  the  pans  for  the  weights  and  the  substance  to  be 
weighed,  will,  on  the  contrary,  lead  to  results  too  high  or  low, 
as  the  case  may  be.  We,  however,  obtain,  in  this  way,  only 
the  relative  weight  of  the  substance,  and  not  its  absolute  weight, 
which  requires  a  perfect  balance. 

Borda  proposes  to  avoid  the  errors  of  inaccurate  balances, 
by  first  taking  the  tare  of  the  substance  with  that  or  any  other 
counterpoise,  and  afterwards  substituting,  in  its  stead,  weights 
sufficient  to  restore  the  equilibrium,  which  was  disturbed  by 
its  withdrawal  from  the  dish.  The  sum  of  these  added  weights 
represent  exactly  that  of  the  substance  being  weighed.    This 


104  WEIGHING  OF  SOLIDS. 

mode  is  termed  double  weighing,  and  affords  very  nice  results 
even  in  balances  with  disproportioned  beams. 

A  modification  of  the  above  method  is,  supposing,  for  in- 
stance, that  five  grains  of  a  substance  are  required,  to  place 
twenty  grains'  weight  in  one  dish,  and  a  small  capsule  in  the 
other,  and  then  to  establish  equilibrium  by  adding,  to  the  lat- 
ter, the  requisite  number  of  very  fine  shot.  This  done,  remove 
15  grains  from  the  first  dish,  and  introduce  into  the  capsule 
sufficient  of  the  substance,  to  be  weighed,  to  compensate  for 
their  loss. 

Weighing  of  Solids. — The  balance  being  in  perfect  order 
and  repose,  the  next  step  is  to  counterpoise  the  vessel  in  which 
the  substance,  which  should  in  no  instance  be  placed  upon  the 
naked  dish,  is  to  be  weighed.  Circular  disks  of  highly  glazed 
paper  are  sometimes  used  as  recipients,  but  being  attractive 
of  moisture,  are  preferably  replaced  by  a  watch  glass  or  cru- 
cible of  platinum  or  of  porcelain.  The  recipient  being  placed 
upon  the  pan,  appropriated  exclusively  for  the  purpose,  is 
then  accurately  counterbalanced  by  shot  or  fragments  of  me- 
tal. In  analyses,  the  counterpoise  must  be  preserved  for 
future  references.  They  may  be  either  wrapped  in  paper 
or  enclosed  in  paper  pill-boxes,  but  in  either  case  must  be 
labelled.  In  delicate  analyses,  to  avoid  error,  the  tare  of  the 
vessel  should  be  estimated  in  weights,  and  their  amount  im- 
mediately noted  down,  to  be  afterwards  subtracted  from  the 
combined  weight  of  it,  and  the  substance  weighed.  The  tare 
of  the  drying  tubes,  or  of  Liebig's  and  other  apparatus  used 
in  organic  analysis  requiring  to  be  weighed,  to  prevent  mis- 
takes, should  be  labelled  upon  the  implements  themselves 
with  which  it  corresponds.  This  done,  the  substance  is  in- 
troduced into  the  recipient,  if  in  lumps,  by  means  of  a  pair 
of  forceps  with  platinum  points;  if  in  powder,  with  an  ivory, 
horn,  or  platinum  spoon  or  spatula,  accordingly  as  it  may  be 
inert  or  corrosive.  The  blade  of  the  spatula  should  never  be 
of  steel,  as  it  is  so  liable  to  oxidation.  A  slip  of  very  thick 
sheet  platinum,  one  inch  in  width  and  two  inches  long,  fast- 
ened in  a  wooden  or  metallic  handle,  is  generally  used.  Its 
usefulness  for  this  purpose  may  be  increased  by  alloying  it 
with  a  very  minute  portion  of  silver,  which  increases  its  elasti- 
city in  an  eminent  degree.  The  weights  are  added  to  the 
opposite  dish,  and  always  after  throwing  the  beam  out  of 
action,  through  the  side  door  of  the  case,  which  must  be  im- 


WEIGHING  OF  COEROSIVE  SUBSTANCES.  105 

mediately  closed  after  each  addition.  If,  when  the  balance  is 
lifted  from  its  supports,  by  depressing  the  thumb  lever 
extending  without  the  case,  the  index  needle  turns  rapidly 
towards  the  dish  opposite  to  the  weights,  the  balance  must  be 
put  in  repose,  another  weight  added,  and  the  motion  of  the 
needle  again  examined.  This  operation  should  be  repeated 
upon  the  addition  of  each  weight,  however  small.  As  the 
pans  approach  equilibrium,  the  vibrations  of  the  needle  de- 
crease in  rapidity,  and  a  little  experience  and  observation 
will  enable  one  to  hit  the  right  point  after  one  or  two  trials. 
When  any  given  quantity  of  a  substance  is  to  be  weighed,  the 
requisite  weight  should  be  placed  in  the  dish  first,  and  the  sub- 
stance if  in  powder  deposited  in  the  other  dish  with  a  spoon 
or  spatula,  until  an  accurate  counterpoise  is  obtained,  taking 
care  however,  to  bring  the  balance  at  rest  upon  each  addi- 
tion of  material,  which  may  be  made  to  fall  in  very  minute 
quantities  from  the  spatula  by  gently  tapping  against  its 
handle  with  the  finger. 

Those  substances  which  are  hygrometric,  should  be  weighed 
in  a  covered  vessel;  for  instance,  between  two  watch  glasses, 
or  in  a  small  tube  with  a  ground  stopper,  which  may  be  held 
in  an  upright  position  by  a  twine  loop  slipped  over  the  sus- 
pending wire  of  the  pan,  or  by  a  cork  and  wire  stand,  as 
shown  by  Fig.  57. 

The  more  delicate  balances  have  for  this  purpose,  for  that 
of  organic  analysis  and  of  weighing  substances  in  water, 
a  supplementary  pan,  with  a  hook  beneath,  for  convenience 
of  suspension.  This  pan,  which  descends  from  the  beam 
only  one-half  the  distance  of  the  other,  is  shown  by  Fig.  62. 

After  the  weighing  is  completed,  the  weights,  as  before 
directed,  are  withdrawn  with  forceps,  placed  upon  a  piece 
of  white  paper,  and  their  several  amounts  added  together ; — 
the  total  gives  the  weight  of  the  substance  in  the  opposite 
dish. 

Covered  vessels  are  also  requisite  for  those  corrosive  sub- 
stances the  exhalations  from  which  would  be  injurious  to  the 
balance,  and  impair  its  accuracy. 

Substances  should  never  be  weighed  whilst  hot,  even  in 
closed  vessels,  otherwise  the  ascending  current  of  air  thus 
produced,  together  with  an  unequal  expansion  of  one  arm  of 
the  beam,  will  give  inaccurate  results.  A  crucible,  therefore, 
which  has  been  over  the  lamp  for  the  ignition  of  its  contents, 
8 


106  WEIGHING  OP  LIQUIDS. 

should  be  first  cooled  by  standing  upon  the  iron  slab  accom- 
panying the  balance  table,  otherwise  its  hot  weight,  not  cor- 
responding with  its  cold  weight,  would,  in  estimating  the  re- 
sult, lead  to  an  error  in  the  real  weight. 

Weighing  of  Liquids. — The  nature  of  liquids,  especially 
their  temperature  and  volatility,  have  an  important  influence 
upon  the  precision  of  the  results. 

Non-volatile  liquids  may  be  weighed  in  a  counterpoised 
capsule,  watch  glass,  flask  or  tube.  Those  vessels  which  have 
spherical  bottoms  are  supported  in  the  pans  upon  cork  rings, 
which  are  readily  made  by  hollowing  out  a  cork  and  bevelling 
its  upper  edges  interiorly.  If  the  recipient  is  tall,  it  requires 
a  stand  to  maintain  it  in  an  upright  position. 
Fig.  57.  This  stand,  shown  by  Fig.  57,  is  nothing  more 
f=^  than  a  disk  of  cork  5,  with  the  wire  catch  a,  fast- 

ened to  it.  An  excellent  substitute,  is  a  broad 
cork,  with  a  hole  in  its  centre,  corresponding  with 
the  size  of  the  tube,  and  bored  smoothly  and 
nearly  through  the  cork  with  the  cork-borer  here- 
after to  be  described.  The  use  of  the  twine  loop, 
before  mentioned,  is  less  safe  and  convenient  for 
suspending  these  vessels. 

The  liquids  are  conveyed  to  the  recipients  in  dropping 
tubes  or  pipettes.  This  mode  allows  their  gradual  addition, 
and  in  small  quantities.  The  pipette,  for  small  quantities,  is 
nothing  more  than  a  tube  of  a  quarter  inch  diameter, 
Fig.  58.  drawn  out  at  its  lower  end,  as  shown  by  Fig.  58. 
The  tapering  end  of  this  tube,  being  placed  in  the 
liquid,  as  soon  as  the  latter  has  risen,  interiorly  to 
its  external  level,  place  the  thumb  upon  the  upper 
orifice  of  the  pipette,  withdraw  it  from  the  liquid, 
and  convey  it  to  the  counterbalanced  recipient  in  the 
scale  dish.  Holding  it  immediately  over  this  reci- 
pient, you  then  remove  the  finger  and  allow  the  liquid 
to  be  driven  out  by  atmospheric  pressure,  either  in 
a  thin  stream  or  drops,  according  as  the  capillary 
orifice  of  the  thin  end  of  the  pipette  is  larger  or  smaller. 
Remember  that,  as  pressure  of  the  surrounding  fluid  is  the 
cause  of  the  liquid's  ascension  into  the  tube,  its  ingress  is 
proportional  to  the  depth  to  which  the  pipette  enters  the 
containing  vessel. 

When  the  pipette  contains  more  liquid  than  the  required 


WEIGHINa  OF  LIQUIDS: — PIPETTES. 


107 


quantity,  the  flow  can  be  arrested  as  soon  as  the  given  weight 
is  counterbalanced,  by  quickly  replacing  the  finger  upon  the 
upper  orifice  of  the  tube.  After  removing  it  from  over  the 
pan,  the  surplus  can  be  emptied  into  the  original  vessel. 

Any  excess  of  the  liquid,  preventing  a  perfect  adjust- 
ment, may  be  removed  from  the  recipient  with  an  empty 
pipette  in  the  same  manner  as  it  was  introduced.  With  a 
little  precaution  in  the  management  of  the  pipette,  the  flow 
may  be  made  so  gradual  that  it  can  be  arrested  as  soon  as  the 
vessel  has  received  the  required  quantity.  The  insertion  of 
slips  of  bibulous  paper  serves  to  withdraw  any  slight  excess, 
unless  the  liquid  is  corrosive  and  acts  upon  paper,  in  which 
case,  a  glass  rod  must  be  substituted.  The  insertion  of  this 
rod  into  the  liquid,  and  its  subsequent  withdrawal,  causes  a 
loss  thereto  of  the  small  adherent  quantity,  and  thus  we  have 
a  means  of  accurately  weighing  any  required  quantity  of 
liquid. 

If  the  quantity  of  liquid  to  be  weighed  is  large,  the 
form  of  the  pipette  must  be  as  shown  by 
Fig.  59.  The  bulb  in  its  centre  serves  as  a  re- 
servoir for  the  required  charge.  If  the  nature 
of  the  liquid  does  not  render  the  operation  dis- 
agreeable to  the  manipulator,  the  pipette  may 
be  quickly  filled  by  suction  with  the  mouth. 
This  plan,  however,  is  objectionable,  as  being 
liable  to  introduce  moisture.  A  much  better 
method  is  to  cover  tightly  the  larger  or  upper 
end  of  the  pipette  with  a  caoutchouc  bottle. 
By  compressing  this  bottle  with  the  hand,  a 
partial  expulsion  of  air  ensues,  and  the  liquid, 
into  which  the  pipette  is  plunged,  rushes  in 
quickly  to  fill  the  vacuum.  The  bottle,  being 
again  distended  by  the  upward  pressure  of  the 
interior  atmosphere,  prevents  the  exit  of  any 
drop  of  liquid,  until  it  is  forced  out  by  com- 
pressing the  bag  a  second  time. 

Some  chemists  prefer  pipettes  of  syringe  con- 
struction, Fig.  60.  Like  the  afore-mentioned,  they  must  be 
invariably  of  glass.  The  liquid  is  drawn  from  its  original 
container  by  immersing  the  taper  end  therein,  and  raising  the 
piston; — the  liquid  mounts  into  the  cylindric  reservoir  until 
filled.     The  depression  of  the  piston,  by  the  pressure  of  the 


■^  s 


Y 


108  WEIGHING  OF  GASES. 

finger  upon  the  top  of  the  handle,  causes  the  exit  of  the  liquid 
with  rapidity  proportional  to  the  power  applied. 

The   stock  of  pipettes   should   consist  of  several 
y    go      sizes.    After  being  used,  they  should  be  carefully  laid 
^^        across  a  porcelain  plate,  there  to  remain  until  the 
completion  of  the  weighing,  when  they  must  be  well 
rinsed  out  previous  to  being  returned  to  their  places 
in  the  drawers. 

All  volatile  substances  must  be  weighed  in  small, 
closely  stoppered  flasks,  tubes  or  other  vessels,  pre- 
viously counterpoised.  To  insure  accurate  results, 
care  must  be  taken  that  the  temperature  does  not 
favor  volatilization.  Fuming  liquids  should,  if  possi- 
ble, be  measured. 

To  preserve  the  balance,  as  much  as  possible,  from 
their  corrosive  action,  the  recipient  should  be  removed 
from  the  pan  upon  each  addition  or  withdrawal  of  any 
portion  of  its  charge,  and  tightly  closed  again  before 
being  returned.  The  slender  tube.  Fig.  99,  for  small 
quantities,  and  the  syringe  for  larger  proportions, 
are  the  proper  implements  for  conveying  the  liquids  to  the 
balance. 

Very  deliquescent  substances,  such  as  are  not  checked  in 
their  liquefying  tendency  by  the  greatest  practicable  dryness 
of  the  balance  case,  and  are  not  alterable  by  water,  should  be 
weighed  in  solution.  First,  pour  in  a  sufficiency  of  water  in 
the  counterpoised  recipient  and  note  its  weight.  The  increase 
of  weight  given  to  this  water  by  the  addition  of  the  deliques- 
cent body,  is  the  actual  weight  of  the  latter,  and  the  solution 
can  be  used  in  the  analysis  instead  of  the  solid.  In  some 
instances,  according  to  the  nature  of  the  substance,  alcohol 
may  be  substituted  for  water. 

Weighing  of  Gases. — In  weighing  gases,  it  is  necessary,  in 
order  to  obtain  nice  results,  to  guard  against  the  least  varia- 
tions of  temperature,  pressure,  and  humidity  of  the  atmo- 
sphere. Gases  are  readily  estimated  by  means  of  a  very  sen- 
sitive balance,  though  the  old  plan,  by  measurement  of  volume 
in  graduated  vessels,  is  accurate  and  easily  executed. 

Gases  are  weighed  in  counterpoised  balloons,  which  must  be 
thoroughly  cleaned  and  dried,  and  wiped  exteriorly  and  inte- 
riorly, so  as  to  remove  every  particle  of  grease,  dirt  or  dust. 
The  balloon  is  then  to  be  connected  by  a  coupling  cock  fitted 


WEIGHING  OP  GASES.  109 

to  its  neck,  with  an  air-pump  (Fig.  32)  or  syringe,  and  ex- 
hausted of  its  air.     To  insure  the  expulsion  of  all  remnants 
of  gas  from  a  former  weighing,  the  balloon  should  be  subjected 
to  repeated  alternate  exhaustions  and  airings.     The  exhausted 
balloon  is  then  to  be  attached  to  a  graduated  bell-glass,  also 
fitted  with  a  coupling  cock,  as  shown  by  Fig.  61.     This  bell- 
glass  is  the  reservoir  of  the  gas  which  is  received  or 
collected  over  {see  Pneumatic  Trough)  water  or  mer-     Fig.  6i. 
cury ;  the  latter  fluid,  giving  more  exact  results,  is 
used  for  those  gases  which  are  soluble  in  the  former. 
Communication  between  the  balloon  and  bell-glass, 
being  made  by  opening  their  connecting  cocks,  the 
gas  rushes  from  the  latter  into  the  former  by  force 
of  atmospheric  pressure  upon  the  mercury.     When 
the   balloon  is  filled,  the  flow  is  to  be  stopped  by 
closing  the  cocks.     A  delay  of  several  minutes  is 
necessary  [see   Measurement   and   Transfer  op 
Gases)  to  allow  the  temperature  within  the  bulb  to 
become  that  of  the  external  air,  that  the  level  within 
and  without  the  bell-glass  may  be  equalized,  and  the 
quantity  of  gas  noted.     The  balloon  must  then  be      fefr"^. 
detached,  and  again  weighed  with  care  and  accu- 
racy.    The  difi'erence  between  its  present  and  original  weight, 
is  that  of  the  volume  of  gas  which  it  contains. 

In  the  weighing  of  gases,  it  is  indispensable  to  note  the 
temperature  and  barometric  pressure,  and  to  observe  all  other 
conditions  and  precautions  requisite  in  the  Measurement  of 
Gases. 

Those  gases  which  are  without  action  upon  mercury,  ought 
to  be  collected  over  that  metal,  for  most  gases,  by  contact 
with  water,  absorb  more  or  less  of  its  vapor,  according  to  the 
temperature,  and,  therefore,  to  insure  correct  results,  it  is 
generally  preferable  to  purify  the  gas  of  moisture  previous  to 
weighing  it.  This  is  done  by  passing  it  through  a  tube  {see 
Desiccation  of  Gases)  containing  fused  chloride  of  calcium, 
or  some  other  absorbent  substance. 

It  must  be  recollected,  however,  in  the  desiccation  of  gases, 
by  transit  through  tubes  containing  absorbent  matter,  that 
the  quantity  of  dry  gas,  entering  into  the  globe,  is  less  than 
that  received  from  the  bell-glass,  the  volume  of  vapor  ab- 
stracted in  its  passage.  To  determine  the  amount  of  this  loss, 
"  observe  the  temperature  of  the  moist  gas,  and  correct  its 


110 


WEIGHING  OF  GASES. 


volume  by  the  pressure  of  thirty  inches  of  mercury.  Then, 
by  the  table  below,  ascertain  the  proportion  of  vapor  which 
was  present  in  the  volume  which  left  the  jar,  and  subtract 
it  from  the  corrected  volume; — the  remainder  will  be  the 
volume  of  dry  gas  which  has  entered  the  globe." 

The  table,  taken  from  Faraday,  "exhibits  the  proportion 
by  volume  of  aqueous  vapor  existing  in  any  gas  standing  over 
or  in  contact  with  water,  at  the  corresponding  temperatures, 
and  at  mean  barometric  pressure  of  thirty  inches." 


40°  — 

.00933 

51°  — 

.01380 

61°  — 

.01923 

71°  — 

.02653 

41  — 

.00973 

52  — 

.01426 

62  — 

.01980 

72  — 

.02740 

42  — 

.01013 

53  — 

.01480 

63  — 

.02000 

73  — 

.02830 

43  — 

.01053 

54  — 

.01533 

64  — 

.02120 

74  — 

.02923 

44  — 

.0:093 

55  — 

.01586 

65  — 

.02190 

75  — 

.03020 

45  — 

.01133 

56  — 

.01640 

66  — 

.02260 

76  — 

.03120 

46  — 

.01173 

57  — 

.01693 

67  — 

.02330 

77  — 

.03220 

47  — 

.01213 

58  — 

.01753 

68  — 

.02406 

78  — 

.03323 

48  — 

.01253 

59  — 

.01810 

69  — 

.02483 

79  — 

.03423 

49  — 

.01293 

60  — 

.01866 

70  — 

.02566 

80  — 

.03533 

50  — 

.01333 

This  table  is  also  useful  for  determining  that  part  of  the  vo- 
lume and  weight  of  a  moist  gas,  due  to  aqueous  vapor  after  it 
has  been  weighed  without  previous  desiccation,  for  as  it  "  in- 
cludes any  temperature  at  which  gases  are  likely  to  be  weighed, 
the  proportions  in  bulk  of  vapor  present,  and  consequently  of 
the  dry  gas,  may  easily  be  ascertained.  For  this  purpose  the 
observed  temperature  of  the  gas  should  be  looked  for,  and 
opposite  to  it  will  be  found  the  proportion  in  bulk  of  aque- 
ous vapor  at  a  pressure  of  30  inches.  The  volume  to  which 
this  amounts  should  be  ascertained  and  corrected  to  mean 
temperature.  Then  the  wliole  volume  is  to  be  corrected  to 
mean  temperature  and  pressure  and  the  corrected  volume  of 
vapor  subtracted  from  it.  This  will  leave  the  corrected  vo- 
lume of  dry  gas.  It  has  been  ascertained,  in  a  manner  ap- 
proaching to  perfect  accuracy,  that  a  cubic  inch  of  perma- 
nent aqueous  vapor  corrected  to  the  temperature  of  60°, 
and  a  mean  pressure  of  30  inches,  weighs  0.1929  grains. 
The  weight,  therefore,  of  the  known  volume  of  aqueous  vapor 
is  now  easily  ascertained,  and  this  being  subtracted  from  the 
weight  of  the  moist  gas,  will  give  the  weight  of  the  dry  gas, 
the  volume  of  which  is  also  known. 

"As  an  illustration,  suppose  a  gas  standing  over  water 
had  been  thus  weighed,  and  that  220  cubic  inches  at  the 


WEIGHING  OF  GASES.  Ill 


temperature  of  50°  Fahr.,  and  barometric  pressure  of  29.4 
inches  had  entered  into  the  globe  and  caused  an  increase  in 
weight  of  101.69  grains.  Bj  reference  to  the  table  it  will 
be  found  that  at  the  temperature  of  50°,  the  proportion  of 
aqueous  vapor  in  gas  standing  over  water  is  .01333,  which  in 
the  220  cubic  inches  will  amount  to  2.933  cubic  inches,  which 
corrected  to  the  temperature  of  60°,  becomes  2.942  cubic 
inches.  The  whole  volume  corrected  to  mean  temperature 
and  pressure  will  be  found  to  equal  219.929  cubic  inches, 
from  which,  if  the  2.942  cubic  inches  of  aqueous  vapor  pre- 
sent be  subtracted,  it  will  leave  216.987  cubic  inches  as  the 
volume  of  dry  gas  at  mean  temperature  and  pressure :  2.942 
cubic  inches  of  aqueous  vapor  weigh  .5675  grains,  for  2.942 
X  0.1929=  0.5675;  this  subtracted  from  101.69,  the  whole 
weight,  leaves  101.1225  grains,  which  is  the  weight  of  the 
216.987  cubic  inches  of  dry  gas;  and  by  the  simple  rule  of 
proportion,  therefore,  it  will  be  found  that  100  cubic  inches 
of  such  gas,  when  dried  and  at  mean  temperature  and  pres- 
sure, will  weigh  46.603  grains. 

^'  It  is  not  necessary  in  this  experiment  that  the  globe  or 
flask  be  perfectly  exhausted  of  air  before  the  gas  be  admit- 
ted, all  that  is  necessary  in  that  respect  being,  that  the  quan- 
tity of  gas  which  enters,  and  the  corresponding  increase  of 
weight,  be  known.  For  the  same  reason  it  is  not  necessary 
that  the  globe  be  filled,  provided  the  quantity  which  does 
enter  is  ascertained  upon  the  graduation  of  the  jar  when  the 
level  is  the  same  inside  and  outside;  and  that  no  alteration 
of  the  quantity  in  the  globe  be  allowed  before  the  weighing 
is  completed.  The  state  and  quantity  of  the  gas  are  estimated 
in  the  jar,  and  it  is  there  that  the  temperature  and  pressure 
should  be  attended  to.  It  is  essentially  necessary  that  the 
temperature  of  the  globe  over  the  water  should  have  been 
steady  for  some  time  before  the  experiment  be  made,  and 
that  it  do  not  change  until  the  gas  has  entered  the  globe  and 
the  stop-cock  is  securely  closed.  After  that,  a  little  varia- 
tion of  temperature  is  of  no  consequence,  so  that  nothing 
passes  into  or  out  of  the  globe  until  the  conclusion  of  the 
experiment.  The  globe,  as  before  said,  should  be  clean  and 
dry." 


112  DETERMINATION  OF  SPECIFIC  GRAVITY. 


CHAPTER   yill. 

THE  DETERMINATION  OF  SPECIFIC  GRAVITY. 

Bodies  which  are  of  uniform  bulk  may  vary  in  density,  and 
thus  give  rise  to  a  difference  in  their  specific  gravity — the  rela- 
tion of  their  weight  to  their  volume.  The  density  of  bodies  is 
estimated  by  certain  standards ;  that  for  solids  being  pure  dis- 
tilled or  rain  water  (=1.000)  at  60°  F.  The  number,  there- 
fore, expressing  the  specific  gravity  of  a  body  is  the  number 
of  times  it  is  heavier  or  lighter  than  an  equal  volume  of  water. 
For  example,  if  two  bodies  of  equal  bulk  differ  in  density 
in  the  ratio  of  one  to  two,  the  latter  is  said  to  have  twice  the 
specific  gravity  of  the  former,  and  so  in  proportion.  There- 
fore, "  the  volumes  being  equal,  the  densities  of  bodies  are 
directly  as  their  weights;  or,  the  weights  being  equal,  the 
densities  are  inversely  as  their  volumes." 

"  Thus,  if  a  cubic  centimetre  of  iron  weighs  7.8,  while  an 
equal  volume  of  water  weighs  only  one  gramme,  7.8  is  the 
specific  gravity  of  iron."  Hence,  to  find  the  density  or  spe- 
cific gravity  of  a  solid  substance,  its  absolute  weight  must  be 
divided  by  the  weight  of  an  equal  volume  of  water. 

Specific  Gravity  of  Solids.  By  means  of  the  Hydro- 
static Balance. — The  two  principal  operations  for  estimating 
the  specific  gravity  of  a  solid  heavier  than  water,  are :  First,  to 
weigh  it  accurately  in  air ;  and  secondly,  to  weigh  it  in  water. 
The  weight  at  each  weighing  must  be  immediately  noted  in 
the  record  book. 

All  of  the  finer  balances  are  provided  with  a  supplementary 
pan  (Fig.  62),  for  these  weighings  in  fluids.  Though  neces- 
sarily but  one-third  the  depth  df  the  regular  pans,  it  is  accu- 
rately made  so  as  to  exactly  counterbalance  either  of  them, 
and  when  adjusted  to  the  beam,  in  its  stead,  to  maintain  per- 
fect equilibrium.  The  hook  beneath  the  pan  is  a  convenience 
for  the  suspension  of  the  body  to  be  weighed.  This  arrange- 
ment permits  the  weighing  of  the  body  in  air,  and  subse- 
quently in  water,  without  disturbing  it  or  the  balance.  The 
process  is  as  follows :  Suspend  the  body  to  be  weighed  by  a 


SPECIFIC  GRAVITY  OF  SOLIDS.  113 

very  fine  platinum  wire  or  unspun  silken  thread,  to  the  hook 
at  the  bottom  of  the  supplementary  pan,  and  adjust  this  dish 
to  that  side  of  the  beam  from  which  the  regular  dish  has  been 
removed  to  give  place  to  it.  There  are  other  substitutes 
for  platinum  and  silk,  but  being  more  permeable  and  less 
capable  of  furnishing  a  very  fine  and  strong  thread,  they  do 
not  afford  such  nice  results  in  delicate  experiments.  This 
done,  take  the  weight  of  the  body  in  air,  observing  the  requi- 
site precision  in  Weighing,  and  note  it  down  in  the  record 
book  without  delay.  To  take  the  weight  in  water,  it  is  now 
only  necessary  to  convey  a  beaker  glass  containing  that 
liquid,  immediately  under  the  dish,  and  carefully  to  immerse 
therein  the  suspended  body.  This  vessel  must  be  of  diame- 
ter sufficient  to  allow  a  free  play  of  the  body  without  contact 
with  its  sides.  Fig.  62,  represents  the  whole  arrangement. 
In  ii^troducing  the  body  into  water,  particu- 
larly if  it  presents  rough  surfaces,  the  air  Fig.  62. 
attaches  itself  in  bubbles,  which  must  be  re- 
moved with  either  a  camel's  hair  pencil  or 
wooden  stick.  These  precautions  being  duly 
observed,  put  the  balance  in  action  and  take 
the  weight  of  the  body,  and  immediately  re- 
cord it.  The  apparent  loss  of  weight  repre- 
sents the  weight  of  the  bulk  of  water  which 
the  body  displaces,  and  hence  we  have  the 
requisite  data  upon  which  to  calculate  its 
specific  gravity,  viz.,  its  weight  in  air  and 
the  weight  of  its  own  bulk  of  water. 
Thus,  for  example,  the  body  weighs : — 

In  air     .         .         .         .         373  grains. 
In  water  ...         341      " 


Loss     .         .  32      " 

By  following  the  rule,  and  dividing  the  total  weight  by  the 
loss  of  weight  in  water,  thus  373  -r-  32,  we  have  1.165  as  its 
specific  gravity  or  density. 

If  the  body  is  lighter  than  water,  a  weight  of  known  mag- 
nitude and  density  is  joined  with  it  to  sink  it.  The  weight 
may  be  a  capsule,  and  form  a  part  of  the  furniture  of  the  ba- 
lance for  this  especial  purpose.  It  should  be  cullendered  to 
allow  the  free  escape  of  the  globules  of  air  adherent  to  the 


114  SPECIFIC  GRAVITY: — HYDROSTATIC  BALANCE. 

body,  after  receiving  which,  it  should  be  suspended  to  the 
short  pan  as  before  directed. 

In  this,  as  in  the  previous  instance,  the  weight  required  to 
re-establish  the  equilibrium  disturbed  by  the  immersion  of  the 
body  in  water,  expresses  the  weight  of  the  volume  of  water 
displaced. 

''The  rule,  therefore,  is — from  the  difference  between  the 
weight  of  the  two  in  water  and  their  weight  in  air,  subtract 
the  difference  between  the  weight  of  the  heavy  solid  in  air  and 
its  weight  in  water ;  the  remainder  is  the  weight  of  a  quantity 
of  water  equal  in  bulk  to  the  light  solid,  from  which  the  spe- 
cific gravity  of  the  substance  may  be  obtained  by  simple  pro- 
portion. 

"As  an  example,  suppose  the  following  case: — 

1.  The  weight  of  the  light  solid  in  air    .     .12  grs. 

2.  The  weight  of  the  heavy  solid  in  air       .  22    " 

3.  The  weight  of  the  heavy  solid  in  water  .  19    " 

4.  The  weight  of  both  tied  together  in  water    8    " 

"Then,  from  the  weight  of  both  in  air  (12  +  22)  34  grs. 
Deduct  the  weight  of  both  in  water  .     .     .     8    " 

26    " 
"And  from  the  remainder  deduct  22— 19=  3       3    " 

"Which  gives  the  weight  of  the  bulk  of  1       qo    a 
water  displaced  by  the  light  body  alone  J 

"  The  following  proportion  then  affords  the  specific  gravity 
of  the  body: — 

as  23  :  12  : :  1.  :  0.5217." 

[Parnell.) 

If  the  substance  is  porous  or  in  powder,  its  specific  gravity 
is  better  estimated  by  weighing  it  in  the  bottle  (Fig.  64),  after 
the  precaution  of  disengaging  all  adherent  globules  of  air ; 
otherwise  it  must,  in  following  the  preceding  process,  be 
weighed  in  a  capsule,  counterpoised  first  in  air  and  afterwards 
in  water.  The  water  also  should,  before  being  used  for  this 
purpose,  be  freed  of  any  contained  air  by  pouring  it  several 
times  from  one  vessel  to  another. 

When  the  body  is  soluble  in  water,  it  must  be  replaced  by 
some  other  liquid  of  determined  specific  gravity,  which  is 
without  action.  Olive  oil,  spirits  of  turpentine  and  alcohol, 
are  applicable,  one  or  the  other,  for  most  cases. 


SPECIFIC  gravity: — STOPPERED  FLASK.  115 

"  The  specific  gravity  of  the  substance  is  then  found  by 
the  following  proportion, — As  the  density  of  water  is  to  the 
density  of  the  liquid  used,  so  is  the  density  of  the  substance 
in  relation  to  the  liquid  in  which  it  is  weighed  as  unity,  to 
its  density  compared  with  water  as  unity." 

"  By  the  above  described  process,  we  find  how  much  a  cer- 
tain quantity  of  fluid  weighs  which  has  the  same  volume  with 
the  body  to  be  weighed,  and  when  once  the  specific  gravity 
of  the  fluid  is  known,  it  is  necessary  to  ascertain  the  weight 
of  an  equal  volume  of  water." 

''  Let  it  be  assumed,  that  a  piece  of  salt,  which  is  insoluble 
in  oil  of  turpentine,  weighs  0.352  gram.,  and  displaces  when 
put  into  the  glass  0.13  gram,  of  oil  of  turpentine.  The  spe- 
cific gravity  of  this  fluid  is  0.8725;  an  equal  volume  of  water 
will  therefore  weigh — " 

0  13 
'         =  0.149,  and  the  specific  gravity  of  the  salt  is,  there- 

The  preceding  mode  of  taking  the  specific  gravity  of  sub- 
stances is  founded  upon  the  Archimedean  law  of  hydrostatics, 
"  that  the  weight  of  a  substance  in  any  medium  is  less  than 
its  absolute  weight,  by  the  weight  of  the  bulk  of  the  medium 
which  it  displaces,  obviously  its  own  bulk."  It  is,  however, 
objectionable,  as  being  liable  to  give  inaccurate  results,  and, 
therefore,  we  proceed  to  speak  of  a  better  method. 

2d.  By  means  of  a  Stoppered  Flash. — In  this  mode  of 
weighing,  which  is  very  available  for  taking  the  density  of 
minute  bulks  of  matter,  and  applies  to  bodies  either  heavier 
or  lighter  than  water,  the  same  attention  to  temperature  is 
requisite,  as  in  the  preceding  process. 

The  glass  bottle  in  which  the  body  is  to  be  weighed,  is  of 
form,  as  shown  by  Fig.  64.     Its  stopper  should  be  round, 
slightly  conical,  and  accurately  ground.    To 
facilitate  the  egress  of  any  excess  of  water,     Fig.  63.     Fig.  64. 
in  case  of  expansion  by  heat,  and  to  enable         ^ 
it  to  sink  to  a  uniform  depth  in  all  posi- 
tions, the  centre  of  the  stopple  should  be 
perforated.     The  precision  with  which  the 
bottle  and  its  stopper  are  manufactured, 
has  an  important  influence  in  bringing  out 


116  SPECIFIC  GRAVITY: — GRAVIMETER. 

an  exact  result.  This  bottle  is  especially  adapted  for  taking 
the  specific  gravity  of  liquids,  and  its  capacity  may  be  from 
100  to  1000  grains  of  distilled  water. 

Three  weighings  are  required  in  taking  the  specific  gravity 
by  this  mode.  The  flask  is  first  filled  with  water,  so  as  to  ex- 
clude all  air,  then  conveyed  to  the  balance  and  accurately 
counterpoised.  The  body  to  be  examined  is  then  placed  in 
the  same  pan  with  the  flask,  and  the  balance  being  again  set 
in  action,  the  weight  of  the  body  is  expressed  by  the  addi- 
tional weight  necessary  to  produce  equilibrium;  and  that  of 
the  body  and  flask  by  the  whole  weight.  The  substance  being 
examined,  is  then  placed  in  the  flask,  which  is  again  weighed, 
after  having  been  wiped  clean,  to  free  it  from  the  displaced 
fluid  which  has  flowed  over  its  sides.  The  third  weighing  is 
to  determine  the  quantity  of  water,  which  is  a  volume  equal 
to  its  own  bulk,  displaced  by  the  immersed  body.  Having 
thus  obtained  the  requisite  data,  we  calculate  as  follows : 

"  The  glass  vessel  with  water  weighs    .         .  13.52    grms. 
The  body 4.056     " 

Both  together 17.576     " 

"  If,  after  throwing  the  body  into  the  bottle,  putting  the 
stopper  in,  and  weighing  the  whole  together,  we  find  it  to  be 
17.316  grammes,  the  weight  of  the  water  forced  out  by  the 
body  must  be  17.576  — 17.316  ==  0.26  gram.;  consequently 

the  specific  gravity  of  the  body  is    '        =  15.6." 

3d.  By  means  of  the  Areometer.  —  The  areometer  is  an 
instrument  which  may  be  conveniently  substituted  for  the 
balance  in  taking  the  specific  gravity  of  solids.  That  known 
as  Nicholson's  is  most  generally  used.  Muller  describes  the 
apparatus  and  the  mode  of  manipulating  with  it,  clearly  and 
concisely,  as  follows: 

"  To  a  hollow  glass  or  metal  body  v,  Fig.  Q^,  a  small  heavy 
mass  I  (a  glass  or  metal  sphere  filled  with  lead)  is  suspended, 
and  superiorly  there  is  attached  to  it  a  fine  stem  supporting 
a  plate  c,  on  which  small  bodies  and  weights  may  be  laid. 
The  instrument  floats  vertically  in  the  water,  because  its 
centre  of  gravity  is  very  low  in  consequence  of  the  weight  I. 
The  instrument  is  so  arranged  that  the  upper  part  of  the  body 


SPECIFIC  GRAVITY  OF  FLUIDS. 


117 


Fig.  65. 


V  projects  above  the  water.  If  now  we  lay  the  body  whose  spe- 
cific gravity  we  would  ascertain  upon  the  plate 
c,  the  instrument  will  descend,  and  by  adding 
additional  weight,  we  may  easily  make  it  sink  to 
the  point  /,  marked  generally  by  a  line  on  the 
rod.  We  remove  the  mineral  or  other  substance 
we  have  been  using,  and  substitute  in  its  place 
as  many  weights  as  will  again  make  the  instru- 
ment sink  to/.  If,  in  the  place  of  the  mineral, 
we  have  had  to  lay  on  n  grains,  the  weight  of 
the  mineral  is  equal  to  n  grains. 

"If,  in  this  manner,  we  have  ascertained  the 
absolute  weight  of  the  mineral,  the  n  grains  must 
be  again  removed,  and  the  body  laid  in  a  basket 
placed  between  v  and  I.  The  instrument  would 
now  again  sink  to  /  if  the  body  laid  in  the  basket  ^ 
had  not  lost  weight  by  being  immersed  in  the  water :  we  must, 
therefore,  lay  on  the  plate  the  weight  m  grains,  that  the  body 
may  be  immersed  to  the  mark.  In  this  manner  we  obtain 
the  absolute  weight  of  the  body  n,  and  the  weight  of  an 
equal  volume  of  water  m ;  the  specific  gravity  we  seek  is, 

therefore. 


n 

m 


"  If,  for  instance,  we  have  to  determine  the  specific  gravity 
of  a  diamond,  we  must  lay  it  on  the  plate  and  add  sufficient 
weight  to  make  the  whole  sink  to  /.  If  we  find  after  remov- 
ing the  diamond,  that  we  must  lay  on  1.2  grains  to  cause  the 
areometer  to  sink  again  to  the  same  point,  the  absolute  weight 
of  the  stone  would  be  1.2  grains.  These  weights  must  be 
again  taken  away  and  the  diamond  laid  in  the  basket ;  then, 
in  order  to  make  the  instrument  sink  to  /,  we  must  add  0.34 
grains  more ;  the  weight  of  a  volume  of  water  equal  in  volume 
to  the  diamond  is,  therefore,  0.34  grains,  and  the  specific 

12 

gravity  required  is  — '-—■  =  3.53." 

Specific  Gravity  of  Fluids. — There  are  three  modes  of 
determining  the  specific  gravity  of  fluids,  taking  precedence 
in  the  order  in  which  we  name  them;  by  the  stoppered  flask, 
the  hydrometer  and  gravimeter.  The  first  method  yields  the 
greatest  accuracy,  and  is  that  used  in  all  nice  investigations. 

By  the  Flask. — Any  small  ground  stoppered  flask  or  vial 


118  SPECIFIC  GRAVITY  BOTTLES. 

will  answer  for  the  purpose.  It  must  first  be  brought  to  the 
temperature  of  60°  F.,  then  accurately  weighed,  and  after 
the  removal  of  the  stopper,  filled  with  distilled  water  of  corre- 
sponding temperature.  The  stopper  is  then  to  be  inserted, 
and  the  water  that  it  displaces  wiped  from  the  sides  of  the 
vessel,  which  when  dry  is  again  carefully  weighed.  Its 
increase  of  weight  expresses  that  of  the  bulk  of  water  which 
it  contains,  and  to  save  time  and  trouble,  should  be  marked 
with  a  diamond  upon  the  neck  of  the  flask  to  serve  for  future 
experiments. 

Glass  flasks  of  this  description  are  made  by  the  manufac- 
turers especially  for  this  purpose.  Their  capacities  are  ar- 
ranged so  as  to  exactly  receive  a  given  quantity  of  distilled 
water  expressible  by  weight  in  round  numbers.  The  sizes 
vary  from  100  to  1000  grs.,  but  in  each  instance  they  have  a 
diamond  scratch  on  their  necks  showing  the  measure  of  their 
contained  weight  of  water.  They  have  been  previously  de- 
scribed at  p.  115,  and  are  represented  by  Figs.  63,  64.  The 
smaller  one  is  most  used  because  of  greater  facility  in  han- 
dling. Moreover  the  quantities  of  fluid  under  examination  are 
generally  limited,  and  hence  the  convenience  of  a  small  flask 
both  on  this  account,  and  because  it  is  more  easily  weighed  in 
a  delicate  balance. 

For  the  more  volatile  liquids,  the  perforated  stopple  should 
be  replaced  by  a  solid  one,  otherwise  loss  by  evaporation  may 
occasion  incorrect  results. 

If  the  chemist  prefers  purchasing  a  flask  to  graduating  one 
himself,  it  must  be  verified  as  above  before  being  used,  and  if 
the  weight  of  its  contents  of  water  does  not  correspond  with 
the  mark  on  the  neck  of  the  flask,  or  of  the  flask  and  water 
combined  with  that  of  the  weight  generally  accompanying  it 
as  a  convenient  counterpoise,  then  the  flask  is  not  to  be  relied 
on,  and  should  either  be  corrected  or  rejected. 

In  either  case  the  flask  must  be  thoroughly  cleansed,  and 
after  each  experiment  should  be  repeatedly  rins6d  with  dis- 
tilled water,  so  that  it  may  be  perfectly  clean  and  dry  when 
wanted  for  the  next  operation.  In  emergencies,  the  interior 
may  be  dried  by  placing  the  flask  upon  the  sand-bath ;  in  this 
case,  however,  it  will  be  necessary  to  allow  its  temperature 
to  fall  again  to  60°  before  using  it. 

Distilled  water  at  60°  F.  is  the  standard  by  which  to  esti- 
mate the  specific  gravity  of  liquids.     To  take  the  density  of 


SPECIFIC  gravity: — HYDROMETER.  119 

a  liquid,  equal  bulks  of  it  and  water  are  taken  at  the  balance. 
The  flask  having  been  graduated,  its  weight  and  that  of  the 
bulk  of  its  contents  of  water  are  already  known ;  it  is,  there- 
fore, only  necessary  to  fill  it  with  the  liquid  under  examination 
at  60°  F.,  to  the  mark  upon  its  neck,  and  after  inserting  the 
stopper,  carefully  weigh  it.  Divide  the  weight  thus  found 
by  the  weight  of  the  water  (as  indicated  on  the  flask)  and  you 
obtain  the  specific  gravity  of  the  liquid.  For  example : — 
The  clean  and  dry  flask  weighs  400  grains, 

do  do         filled  with  pure  water,  at  60°    900      " 

Deduct  the  first  from  the  latter  and  you  obtain  the  weight  of 
the  water  =  500.  Supposing,  then,  that  the  same  bulk  of 
the  liquid  weighs  412  grains,  then  412  -j-  500  =  0,824  its 
specific  gravity. 

If  the  capacity  of  the  flask  is  1000  grains  of  water,  and  one 
of  that  size.  Fig.  63,  may  well  be  used,  when  the  stock  of  the 
liquid  under  examination  is  not  limited,  the  process  is  still 
easier.  It  is  then  only  necessary  to  fill  it  with  the  fluid  and 
weigh  it.  The  weight  obtained  expresses  its  specific  gravity; 
thus,  taking  mercury  for  example,  a  bulk  of  that  metal  equal 
to  the  bulk  of  1000  grains  of  water,  is  13,500  grains,  and, 
therefore,  these  latter  numbers  express  its  density,  taking  care 
to  advance  the  decimal  point  three  figures  to  the  left,  if  the 
water  is  taken  as  1  instead  of  1.000. 

The  vessel  must,  previous  to  weighing,  be  invariably  wiped 
dry  exteriorly  with  a  linen  cloth,  and  to  avoid  any  commu- 
nication of  heat  from  the  hands,  they  should  be  gloved. 

For  determining  the  density  of  very  minute  quantities  of 
rare  liquids,  it  will  be  necessary  to  have  the  aforementioned 
bottles  of  miniature  dimension,  or  else  to  replace  them  by  glass 
bulbs. 

If  the  fluid  is  volatile  and  readily  vaporizable,  it  should,  in 
being  raised  to  the  proper  temperature,  be  heated  over  a 
spirit  lamp,  in  a  test  tube  ;  taking  care  to  keep  the  finger  over 
its  mouth,  during  the  heating  and  cooling,  so  as  to  prevent 
its  being  unclosed. 

By  the  Hydrometer. — Hydrometers  do  not  give  very  accu- 
rate results,  but  they  are  convenient  when  time  is  an  object, 
and  no  great  precision  is  requisite.  Their  action  is  based  upon 
the  hydrostatic  law,  "  that  a  floating  body  displaces  its  oivn 
weight  of  the  liquid  in  which  it  swims.'' 


120 


SPECIFIC  gravity: — HYDROMETERS. 


The  instrument  consists  of  a  glass  stem  A^  with  an  air 
bulb,  jB,  beneath,  properly  ballasted  with  mercury  or  shot,  D. 
The  depth  to  which  the  hydrometer  will 
Fig.  66.    Fig.  67.      gink  in  a  liquid  is  proportional  to  its  rarity, 
for  the  denser  the  liquid,  the  less  of  it  will 
be  displaced.     A  properly  graduated  scale 
inserted  within  the  stem  or  spindle,  allows 
the  appreciation  of  the  density  of  a  liquid 
by  the  greater  or  less  depth  to  which  it 
sinks  therein.     The  form  of  this  instrument 
is  shown  by  Figs.  ^^^  67.     They  are  con- 
structed (Morjit's  Applied  Chemistry)  with 
different  scales  accordingly,   as  they   are 
intended  for  liquids  rarer  or  denser  than 
water.     The   scales   for   those  which  are 
rare  run  from  zero  (at  the  bottom  of  the 
stem)  upwards.   The  graduation  of  the  scale 
for  liquids  denser  than  water  is  reversed. 
Areometers  are  variously  graduated  for  diflferent  liquids, 
thus — 

Those  for  ether  mark  upwards  from  10  to  50° 

"       "   spirits     "  "  "  10  to  80 

"       "   salts        "    downwards  "       0  to  40 
"       "   acids       "  "  "       0  j:o  75 

"       "   syrups    "  "  "       0  to  36 

The  following  table  shows  the  specific  gravity  numbers  cor- 
responding with  Baume's  areometric  degrees  : — 


^ 


HYDROMETERS — MANNER  OP  USING. 


121 


Liquids  denser  than  water. 

Less  dense  than  water. 

05  bo 

i 
1 

1 

i 

■p 

t 

Ofc  bo 

0 

1.0000 

26 

1.2063 

52 

1.5200 

10 

1.0000 

36 

0.8488 

1 

1.0066 

27 

1.2160 

53 

1.5353 

11 

0.9932 

37 

0.8439 

2 

1.0133 

28 

1.2258 

64 

1.5510 

12 

0.9865 

38 

0.8391 

3 

1.0201 

29 

1.2358 

55 

1.5671 

13 

0.9799 

39 

0.8343 

4 

1.0270 

30 

1.2459 

56 

1.5833 

14 

0.9733 

40 

0.8295 

5 

1.0340 

31 

1.2562 

57 

1.6000 

15 

0.9669 

41 

0.8249 

6 

1.0411 

32 

1.2667 

58 

1.6170 

16 

0.9605 

42 

0.8202 

7 

1.0483 

33 

1.2773 

59 

1.6344 

17 

0.9542 

43 

0.8156 

8 

1.0556 

34 

1.2881 

60 

1.6522 

18 

0.9480 

44 

0.8111 

9 

1.0630 

35 

1.2992 

61 

1.6705 

19 

0.9420 

45 

0.8066 

10 

1.0704 

36 

1.3103 

62 

1.6889 

20 

0.9359 

46 

0.8022 

11 

1.0780 

37 

1.3217 

63 

1.7079 

21 

0.9300 

47 

0.7978 

12 

1.0857 

38 

1.3333 

64 

1.7273 

22 

0.9241 

48 

0.7935 

13 

1.0935 

39 

1.3451 

65 

1.7471 

23 

0.9183 

49 

0.7892 

14 

1.1014 

40 

1.3571 

66 

1.7674 

24 

0.9125 

50 

0.7840 

15 

1.1095 

41 

1.3694 

67 

1.7882 

25 

0.9068 

51 

0.7807 

16 

1.1176 

42 

1.3818 

68 

1.8095 

26 

0.9012 

52 

0.7766 

17 

1.1259 

43 

1.3945 

69 

1.8313 

27 

0.8957 

53 

0.7725 

18 

1.1343 

44 

1.4074 

70 

1.8537 

28 

0.8902 

54 

0.7684 

19 

1.1428 

45 

1.4206 

71 

1.8765 

29 

0.8848 

55 

0.7643 

20 

1.1515 

46 

1.4339 

72 

1.9000 

30 

0.8795 

56 

0.7604 

21 

1.1603 

47 

1.4476 

73 

1.9241 

31 

0.8742 

57 

0.7656 

22 

1.1692 

48 

1.4615 

74 

1.9487 

32 

0.8690 

58 

0.7526 

23 

1.1783 

49 

1.4758 

75 

1.9740 

33 

0.8639 

59 

0.7487 

24 

1.1875 

50 

1.4902 

76 

2.0000 

34 

0.8588 

60 

0.7449 

25 

1.1968 

51 

1.4951 

35 

0.8538 

61 

0.7411 

The  hydrometer  is  used  with  a  tall  glass  jar  (Fig. 
68),  which  serves  as  a  recipient  for  the  liquid  to  be 
tested.  After  having  perfectly  cleansed  it  of  grease 
and  dirt  with  a  cloth,  it  is  to  be  placed  in  the  jar  and 
the  liquor,  first  brought  to  60°  F.,  added.  When  it 
becomes  stationary,  note  the  degree  at  which  it 
stands.  For  verification,  raise  it  an  inch  or  more 
out  of  the  liquid  and  then  let  it  gradually  sink  back 
again.  If  it  reaches  the  same  point  as  before,  the 
first  observation  was  correct.  In  reading  the  divi- 
sions on  the  scale,  do  not  take  that  line  where  the 
liquid  rises  in  wetting  the  stem  of  the  instrument, 
but  note  it  at  the  real  level,  which  is  the  curvature 
9 


Fig.  68. 


122  NICHOLSON'S  GRAVIMETER. 

produced  by  the  ascending  motion  of  the  liquid  against  the 
sides  of  the  spindle. 

The  hydrometers  graduated  by  Baume's  process  are  gene- 
rally used.  Those  made  by  F.  A.  Greiner  &  Co.,  Berlin,  are 
the  most  reliable. 

For  information,  in  detail,  upon  the  construction  of  the 
different  kinds  of  hydrometers,  see  Encyclopoedia  of  Qhemistry^ 
and  M'Culloch's  ''Investigations  relative  to  Cane  Sugar  and 
Report  on  Hydrometers.'' 

By  Nicholson's  G-ravimeter.  — "  The  specific  gravity  of 
liquids  may  also  be  determined  by  Nicholson's  areometer. 
Fig.  65.  As  the  instrument  always  sinks  so  far  that  its 
weight,  added  to  the  weight  upon  the  plate,  is  equal  to  the 
mass  of  liquid  displaced,  we  may,  by  the  aid  of  this  instru- 
ment, ascertain  ho^w  much  a  definite  volume  of  water  weighs. 
It  is  necessary,  however,  to  know  the  weight  of  the  instru- 
ment itself.  Suppose  this  weight  to  be  n,  we  must  lay  on 
some  additional  weight  to  make  the  instrument  sink  to/;  if 
we  designate  this  addition  by  a,  then  is  n  •{■  a  the  weight  of 
water  displaced. 

"If  we  immerse  the  instrument  in  another  liquid,  we  must 
lay  on  another  weight  b  in  the  place  of  6f,  to  make  the  whole 
sink  to  f;  b  will  be  greater  than  a  if  the  liquid  be  denser, 
and  less  than  a  if  it  be  lighter  than  water.  The  weight  of 
the  liquid  displaced  is  n  -\-  b;  but  its  volume  is  exactly  as 
great  as  the  volume  of  the  mass  of  water,  whose  weight  is 
7^  -h  «,  because  the  areometer  has  sunk  equally  deep  in  both 
cases. 

"  Suppose  the  instrument  weigh  70  grains,  we  must  add  20 
grains  to  make  it  sink  in  water,  and  1.37,  that  it  may  sink 
to  the  point/  in  spirits  of  wine  ;  then  the  specific  gravity  of 

spirits  of  wine  is  ^^        '  ^  =  0.793." 
^  70+20 

Specific  Gravity  of  Gases. — The  extreme  lightness  of 
gases  and  vapors  renders  it  inconvenient  to  compare  their 
weight  with  that  of  an  equal  bulk  of  water,  and  consequently 
air  is  taken  as  the  standard. 

The  mode  of  taking  these  specific  gravities  is  thus  con- 
cisely and  clearly  described  by  Parnell,  "  From  the  careful 
experiments  of  Br.  Prout,  it  appears  that  100  cubic  inches 
of  atmospheric  air  deprived  of  carbonic  acid  and  aqueous 
vapor  weighs  31.0117  grains,  at  30  inches  of  the  barometer, 


SPECIFIC  GRAVITY  OP  GASES.  123 

and  at  the  temperature  of  60°  F. ;  from  which  observation  it 
is  easy  to  calculate  the  absolute  weight  of  any  bulk  of  a  gas 
from  its  specific  gravity.  Thus  the  specific  gravity  of  chlo- 
rine is  found  to  be  2.47 ;  to  find  how  much  100  cubic  inches 
of  that  gas  weigh  at  mean  temperature  and  pressure,  we 
make  use  of  the  proportion, 

asl.  :  2.47  ::  31.01  :  76.59; 
therefore  100  cubic  inches  of  chlorine  weigh  76.59  grains. 

"  The  simplest  method  of  obtaining  the  specific  gravity  of 
a  gas  is  the  following: — The  object  is  to  ascertain  the  weight 
of  a  bulk  of  gas  equal  to  the  bulk  of  a  known  weight  of  air. 
For  this  purpose,  a  light  glass  globe,  furnished  with  a  stop- 
cock, is  very  accurately  weighed,  when  full  of  air;  then  ex- 
hausted of  its  air,  by  connecting  it  with  an  air-pump,  and 
weighed  in  the  vacuous  state.  The  weighjt  of  the  air  with- 
drawn by  the  exhaustion  is  thus  ascertained.  The  globe,  still 
vacuous,  is  connected  with  a  jar  containing  the  gas  which  is 
to  be  weighed,  at  the  water  or  mercurial  trough ;  the  jar  hav- 
ing a  stop-cock  at  its  top,  into  which  the  stop-cock  of  the 
globe  can  be  screwed  air-tight.  On  gently  opening  both 
stop-cocks,  a  quantity  of  gas  rushes  from  the  jar  into  the  ex- 
hausted globe,  equal  in  bulk  to  the  air  withdrawn  by  the 
exhaustion,  if  the  surface  of  the  liquid  within  the  jar  be 
brought  to  the  level  of  that  without  in  the  trough,  and  the 
temperature  of  the  air  and  the  barometric  pressure  have  not 
varied  during  the  experiment.  The  stop-cock  being  closed, 
the  globe  is  detached  from  the  jar,  and  weighed.  The  dif- 
ference between  its  weight  when  containing  the  gas,  and  when 
vacuous,  is  the  weight  of  a  bulk  of  the  gas  equal  to  the  bulk 
of  air  whose  place  it  occupies,  the  weight  of  which  has  already 
been  determined. 

"  Suppose  the  globe  to  lose  10.33  grains  by  exhaustion  of 
air,  and,  when  exhausted,  to  gain  15.78  grains  by  admitting 
carbonic  acid  gas;  then,  assuming  1.  as  the  density  of  air, 
we  have  the  proportion, 

as  10.33  :  15.78  : :  1.  :  1.527; 
the  specific  gravity  of  carbonic  acid  gas  is,  therefore,  1.527. 

"  Although  thus  simple  in  principle,  the  operation  in  its 
details  is  one  of  extreme  delicacy.  From  the  facility  with 
which  gases  undergo  a  change  in  their  bulk  through  variations 
of  temperature  and  pressure,  it  is  obvious  that  if  the  tempera- 
ture and  barometric  pressure  vary  during  the  course  of  the 


124  SPECIFIC  GRAVITY  OF  GASES. 

experiment,  corrections  must  be  made.  As  an  illustration  of 
the  necessary  corrections,  suppose  the  bulk  of  air  to  weigh 
12  grains  at  the  temperature  of  60°  F.,  and  under  a  pressure 
of  30  inches  bar. ;  and  the  same  bulk  of  the  gas  whose  density 
is  required  to  weigh  20  grains,  but  at  the  temperature  of  50° 
F.,  and  under  a  pressure  of  28  inches  bar.  The  points  to  be 
determined  here  are  two  : — 

"  1.  Considering  the  volume  of  the  air  withdrawn  and  the 
gas  admitted  as  1.,  at  the  observed  temperatures  and  pres- 
sures, what  would  be  the  volume  of  the  gas  at  the  temperature 
and  pressure  at  which  the  air  was  weighed? 

"  And,  2,  having  obtained  that  volume,  what  is  the  cor- 
responding increase  or  reduction  in  the  weight  of  the  gas? 

"  Performed  according  to  rules  which  are  given  in  the  note 
below,*  the  results  of  these  calculations  are  as  follows: — 

"  (a)  A  volume  of  gas  equal  to  1.  at  50°  F.  is  equal  to  1.019 
at  60°  F. 

"  (5)  A  volume  of  gas  equal  to  1.019  at  28  inches  of  the 
barometer  is  equal  to  0.951  at  thirty  inches. 

"A  volume  of  the  gas,  therefore,  equal  to  0.951  weighs  20 
grains ;  a  volume  of  air  equal  to  1.  at  the  same  temperature 
and  pressure  weighing  12  grains.  Then,  if  0.951  vol.  weighs 
20  grains,  1  vol.  should  weigh  21.03  grains:  and 

as  12:  1::  21.03:  1.75; 
1.75  is,  therefore,  the  density  required.  , 

*  "  1.  For  Changes  in  Bulk  by  Pressure. — The  volume  which  a  gas  should 
possess  at  one  pressure  may  be  calculated  from  its  known  volume  at  another 
pressure,  by  the  use  of  the  following  proportion : — As  the  pressure  to  which 
the  gas  is  to  be  corrected  is  to  the  observed  pressure,  so  is  the  observed  volume 
to  the  volume  required.  In  the  example  in  the  text  (6),  the  pressure  to  which 
the  gas  is  to  be  reduced  is  30  inches,  the  observed  pressure  28  inches,  and  the 
volume  is  1.019.     Then,  as  30  :  28  : :  1.019  :  0.951. 

"  2.  For  Changes  in  Bulk  by  Temperature. — From  the  very  recent  experiments 
of  M.  Regnault,  it  appears  that  a  volume  of  gas  expands  by  heat  ^^^  of  its  bulk 
for  each  degree  Fahrenheit.  Hence,  the  volume  of  a  gas  at  0°  F.  being  1,  at 
any  higher  temperature  it  is  found  by  the  formula  1  -j — ^— -•  The  de- 
termination of  the  volume  of  a  gas  at  one  temperature  from  its  known  volume 
at  another  temperature  maybe  attained  by  the  following  formula: — Let  f  be 
the  temperature  Fahrenheit  at  which  the  volume  of  the  gas  is  observed ;  t'  the 
temperature  Fahrenheit  to  which  the  volume  of  the  gas  is  to  be  reduced  j  x  the 
observed  volume  at  t;  and  a/  the  volume  at  t'  required; 

Then  0/  =  ^-^^9 +  0-21^. 
459  4- f 
"  3.  It  is  frequently  necessary  to  combine  corrections  both  for  temperature 
and  pressure.     In  such  a  case,  as  in  the  example  in  the  text,  the  reduction  of 
volume  is  first  made  for  temperature,  and  that  corrected  volume  is  afterwards 
reduced  according  to  the  pressure. 


SPECIFIC  GRAVITY  OF  GASES.  125 

"  The  state  of  dryness  of  a  gas  is  another  circumstance 
which  interferes  with  its  volume ;  for  which  reason,  due  care 
should  be  taken  to  insure  either  the  perfect  dryness  of  the 
gas,  or  its  complete  saturation  with  moisture.  In  the  latter 
case,  the  temperature  must  be  noticed,  and  the  observed 
volume  reduced  according  to  the  proportion  of  aqueous  vapor 
capable  of  existing  in  the  gas  at  the  observed  temperature. 
The  proportions  of  vapor  by  volume  contained  in  1  vol.  of  the 
saturated  gas  for  temperatures  between  40°  and  80°  F.  are 
expressed  in  the  table  at  page  110.  A  cubic  inch  of  aqueous 
vapor  corrected  to  the  temperature  of  60°,  and  at  a  pressure 
of  30  inches,  weighs  0.1929  grains. 

"  The  preceding  method  of  obtaining  the  density  of  a  gas 
still  requires  a  slight  correction  from  another  circumstance, 
when  the  temperature  and  pressure  differ  considerably  at  the 
time  of  weighing  the  air  and  at  the  time  of  weighing  the  gas ; 
but  one  so  trifling  that  it  may,  in  general,  be  neglected. 
The  necessity  of  this  correction  arises  from  the  impossibility 
of  obtaining  a  perfect  vacuum  in  the  globe ;  and  the  remain- 
ing small  quantity  of  air  may  occupy  a  different  space  when 
weighed  with  the  gas,  to  that  which  it  occupied  when  the 
globe  was  weighed  with  air ;  and  consequently,  the  bulk  of 
the  gas  admitted  into  the  globe  is  not  the  same  as  the  bulk  of 
the  air  withdrawn.  If  the  amount  of  rarefaction  of  the  air 
in  the  exhausted  flask  is  observed,  by  means  of  a  barometer 
gauge  attached  to  the  air-pump,  the  amount  of  the  remaining 
air  may  be  calculated  when  the  weight  of  the  quantity  with- 
drawn is  ascertained ;  then  the  alteration  to  which  it  would 
be  subject  in  bulk  by  changes  of  temperature  and  pressure 
may  also  be  estimated,  and  a  due  allowance  made  on  the  bulk 
of  the  gas  admitted  into  the  globe." 

When  the  gas  is  corrosive  in  its  action,  as  in  the  case  of 
chlorine,  the  balloon  with  its  metallic  cock  must  be  replaced 
by  a  glass  flask  with  a  nicely  fitting  ground  stopper.  This 
flask  is  to  be  adjusted  to  a  drying  tube  connected  with  the 
vessel  in  which  the  chlorine  is  generated.  The  bent  end  of 
the  drying  tube  entering  the  flask  should  reach  to  its  bottom. 
The  disengaged  gas  in  passing  through  the  tube  parts  with 
its  moisture,  and  reaching  the  flask  descends  to  the  bottom, 
and  displaces  the  air,  which  is  expelled  through  the  interstices 
at  the  mouth  around  the  tube.  When  the  chlorine  itself  be- 
gins to  escape,  it  is  evidence  that  all  the  air  has  been  dis- 


126 


SPECIFIC  GRAVITY  OF  VAPORS. 


placed,  and  the  flask  is  then  to  be-  slowly  and  gently  detached 
from  the  apparatus  and  hermetically  closed  with  its  ground 
stopper. 

Specific  Gravity  of  Vapors. — There  are  two  modes  of  de- 
termining the  specific  gravity  of  vapors,  the  one  devised  by 
Gay  Lussac  (Pelouze  and  Fremy's  Qhimie  Gfenerale^  vol.  ii., 
Traite  de  Manipulations  Ohimiques,  par  A.  Bobiere,  vol.  ii. 
p.  467),  and  the  other  the  preferable  one  of  Dumas.  It  is  as 
follows  : 

Take  a  glass  globe  of  about  12  to  16  oz.  capacity,  with  a 
long  slender  neck,  wash  it  with  distilled  water,  and  carefully 
dry  it,  either  by  slight  warmth  or  by  means  of  the  exhausting 
syringe  and  chlorcalcium  tube,  Fig.  69.     After  the  balloon  is 

Fig.  69. 


^^mwxE 


^'^^ 


^ 


perfectly  dry,  its  neck  is  to  be  drawn  out  to  a  narrow  tube  6 
or  8  inches  long,  and  bent  nearly  at  a  right  angle,  as  shown 
at  a,  Fig.  70.  The  tip  is  then  to  be  removed  with  a  file,  and 
the  mouth  of  the  tube  rounded  (not  closed)  over  the  blow-pipe 
flame.  The  globe  full  of  air  is  now  weighed,  with  great  pre- 
cision, and  afterwards  warmed  to  expel  a  portion  of  its  air. 
This  done,  its  beak  is  immediately  dipped  into  the  liquid  or 
melted*  solid  matter,  and  as  the  air  within  contracts  by  the 
cooling  of  the  bulb,  which  may  be  hastened  by  dropping  ether 
on  its  exterior,  the  fluid  is  drawn  up.     When  the  requisite 

*  If  the  solid  body  is  not  fusible,  a  given  weight  of  it  is  introduced  into  the 
globe,  previously  dried.  The  neck  is  then  drawn  out,  the  end  removed  and 
placed  in  the  balance.  By  deducting  its  weight  from  that  of  the  whole  balloon, 
you  obtain  the  weight  of  the  balloon  full  of  air. 


SPECIFIC  GRAVITY  OP  VAPORS. 


127 


quantity,  say  100  to  150  grains,  has  entered,  the  globe  is  at 
once  enclosed  in  a  wire  basket  6,  Fig.  70,  and  introduced  into 

Fig.  70. 


a  water,  saline,  metallic  or  other  bath,  the  temperature  of 
which  exceeds  the  boiling  point  of  the  liquid,  50°  or  60°.  The 
wooden  support  e,  to  an  arm  of  which  is  suspended  the  ther- 
mometer c,  keeps  the  globe  firmly  fixed  in  the  bath. 

The  bath  is  brought  to  ebullition,  and  as  soon  as  it  rises 
above  the  boiling  point  of  the  substance,  a  jet  of  vapor  escapes 
through  the  tube,  and  as  soon  as  it  ceases,  the  point  is  sealed 
up  over  the  blow-pipe  flame,  observing  at  the  same  time  the 
temperature  of  the  bath  and  the  barometric  pressure. 

The  globe  thus  closed  is  then  withdrawn  from  the  bath, 
washed,  dried,  and  again  weighed. 

To  determine  the  capacity  of  the  balloon,  its  tube  is  dipped 
into  mercury,  and  its  point  broken  under  the  surface  of  the 
metal,  which  immediately  rushes  in  and  fills  the  vacuum  caused 
by  the  condensation  of  the  vapor,  and  should  occupy  the  whole 
interior.  It  is  evident  that  the  volume  of  mercury  represents 
the  volume  of  the  vapor  at  the  noted  temperature,  and  this 
volume  is  determined  by  transferring  the  mercury  to  a  gradu- 
ated tube,  and  marking  the  number  of  cubic  inches  or  centi- 
metres which  it  occupies. 

We  thus  have  all  the  data  necessary  for  calculating  the 
specific  gravity  of  the  vapor,  having  determined,  experi- 
mentally,— 


128  MEASURES  AND  MEASURING. 

"1.  The  weight  of  the  globe  and  air  at  ordinary  tempera- 
ture and  pressure; 
"2.  The  weight  of  the  globe  and  vapor  filling  it  at  the 
temperature  of  the  bath,  ^nd  under  ordinary  pres- 
sure; and, 
"  3.  The  capacity  of  the  globe. 
"  Having  these  results,  we  obtain  by  calculation, — 

"1.  The  weight  of  the  empty  globe  (by  knowing  the  capa- 
city of  the  globe,  the  weight  of  the  air  filling  it  can 
be  calculated,  which,  deducted  from  the  weight  of 
the  globe  and  air,  leaves  the  weight  of  the  globe 
when  vacuous); 
.  "2.  The  weight  of  vapor  filling  the  globe  at  the  tempera- 
ture of  the  bath  (by  deducting  the  weight  of  the  empty 
globe  from  the  weight  of  the  globe  and  vapor) ;  and, 
"  3.  The  weight  of  air  filling  the  globe  at  the  temperature 
of  the  bath,  and  at  the  pressure  at  which  the  globe 
was  sealed  with  the  vapor. 
"  The  last  calculation  is  made  according  to  rules  given  in 
the  note,  page  124;  having  performed  which,  the  density  of 
the  vapor  required  is  obtained  by  the  simple  proportion, — As 
the  weight  of  air  filling  the  globe  at  the  temperature  of  the 
bath  is  to  the  weight  of  vapor  filling  the  globe  at  the  same 
temperature,  so  is  1  to  the  density  required." 


CHAPTER    IX. 

MEASURES  AND  MEASURING. 

Measuring  of  Fluids. — When  great  accuracy  is  required 
in  the  estimation  of  fluids,  their  weight  is  determined;  but  in 
ordinary  operations,  the  amount  of  their  volumes  is  obtained 
by  the  employment  of  vessels  purposely  prepared  and  gradu- 
ated with  care  and  precision. 

These  vessels  or  graduates  as  they  are  called,  are  gene- 
rally of  two  forms,  those  for  the  larger  operations  being 
cylindrical,  as  shown  by  Fig.  71.  This  shape  combines  both 
strength  and  convenience.    For  the  smaller  (ounce  or  drachm) 


MBASURINa  OF  FLUIDS. 


129 


graduates,  the  conical  form,  Fig.  72,  is  preferable,  as  giving 
greater  facility  by  its  smaller  surfaces,  for  accurately  esti- 
mating minute  volumes. 

Fig.  71.  Fig.  72.  Fig.  73.  Fig.  74. 


G-raduation, — For  the  large  measures,  the  imperial  pint  is 
the  usual  integer.  To  graduate  a  vessel  to  this  extent,  take 
a  glass  balloon.  Fig.  73,  counterbalance  it  and  weigh  therein 
accurately  one  pint  imperial  (8750  grs.)  of  distilled  water,  at 
the  temperature  of  62°  F.,  and  at  30  inches  of  barometric 
pressure.  After  the  vessel  has  remained  undisturbed  upon  a 
level  shelf,  suflficiently  long  for  its  contents  to  acquire  a  smooth 
steady  surface,  scratch  upon  the  neck  the  exact  level  to  which 
the  liquid  rises.  The  narrower  the  neck  of  the  flask  the 
greater  the  facility  in  noting  this  point  without  liability  of 
error.  This  weighed  quantity  of  water  is  then  to  be  trans- 
ferred to  the  proof  glass,  under  process,  either  of  such  a  form 
as  shown  in  Fig.  71,  or  in  Fig.  74,  the  latter,  however,  being 
shorter  and  wider,  is  preferable  for  large  sized  graduates. 
After  the  water  has  settled,  and  presents  a  smooth  calm  sur- 
face, scratch  its  level  accurately  upon  the  exterior  of  the  glass, 
either  with  a  diamond  point  or  a  sharp  file.  Thus  you  obtain 
a  pint  measure,  to  graduate  which  into  its  subdivisions  of 
ounces  and  drachms,  it  is  only  necessary  to  take  the  pro  rata 
weights  of  the  fractions  of  the  pint,  and  proceed  in  manner 
as  above  directed.  So  likewise,  the  vessel  can  be  graduated 
to  pint  divisions,  in  number  as  many  as  its  capacity  will  ad- 
mit, by  multiplying  the  weights  of  water,  and  adding  them  to 
those  previously  measured,  noting  the  level  of  each  with  the 
diamond. 

The  imperial  pint  is  larger  than  the  wine  pint  of  16  fluid- 


130  GRADUATION  OP  VESSELS. 

ounces,  in  the  ratio  of  6  to  5,  and,  therefore,  its  subdivisions 
must  number  20.  This  makes  a  discrepancy,  the  inconve- 
nience of  which  can  be  remedied  by  having  a  second  scale 
upon  the  same  glass,  showing  their  relative  values.  The  only 
disadvantage  is  the  trouble  of  a  second  graduation,  which  is, 
however,  compensated  for  in  the  convenience  of  the  first  scale, 
each  division  of  which,  unlike  the  fluidounce  of  the  wine  pint, 
represents  a  fluidounce  exactly,  weighing  one  ounce  avoir- 
dupois of  distilled  water. 

The  plan  of  graduating  the  pint,  itself  estimated  as  above, 
into  its  subdivisions  by  apportioning  its  height  into  the  requi- 
site number  of  equal  parts,  by  means  of  a  rule,  will  only 
answer  for  vessels  of  uniform  diameter  throughout,  and  which 
are  only  intended  for  the  grosser  operations  of  measuring. 

Those  graduates,  which  are  intended  for  nice  purposes, 
should  also  have  a  third  scale  graduated  in  cubic  inches. 
The  cubic  inch  equals  252.458  grains  of  distilled  water,  at 
temperature  and  pressure  the  same  as  above.  As  there  is 
sufficient  room  upon  the  glass  for  all  of  these  scales  without 
the  necessity  of  crowding  them  together — there  should  be  an 
equal  interval  between  them. 

To  graduate  a  vessel  to  the  litre  of  the  French  standard, 
substitute  1  kilogramme  for  the  8750  grains  distilled  water, 
and  proceed  as  above,  making  the  subdivisions  pro  rata. 

The  graduates  and  cubic  inch  bottles  are  less  to  be  relied 
on  when  purchased  than  when  carefully  graduated  by  the 
operator  himself,  and  they  should  never  be  used  in  important 
experiments  without  having  been  previously  verified. 

For  the  graduation  of  the  ounce  and  drachm  measures,  and, 
indeed,  all  vessels  of  small  diameters  and  capacities  such  as 
tubes  and  the  like,  the  divisions  of  which  must  necessarily  for 
want  of  space  closely  approximate  to  each  other,  mercury  is 
much  preferable  to  water.  Mercury  gives  a  more  level  and 
distinct  surface  than  water,  and  not  being  attracted  by  the 
sides  of  the  vessel,  allows  a  greater  accuracy  in  making  the 
subdivisions,  especially  in  very  narrow  tubes.  The  addition 
of  one  grain  of  lead  to  every  4000  grains  of  quicksilver  im- 
proves the  mercury  for  this  purpose,  but  it  must  be  otherwise 
pure  and  free  from  dross  and  film.  A  cubic  inch  of  pure 
mercury,  according  to  Faraday,  weighs  3425.35  grains,  at 
62°  F. 

There  should  be  a  series  of  these  graduated  glasses,  ranging 
from  a  double  pint  down  to  a  drachm. 


GKADUATION  OP  TUBES.  131 

For  the  tubes  and  other  vessels  used  in  analytic  research, 
the  decimal  divisions  are  both  convenient  and  necessary.  If 
a  cubic  inch  is  to  be  divided  into  tenths  and  hundredths,  the 
former  are  graduated  by  the  space  occupied  in  the  tube  by 
the  one-tenths  (342.50  grs.)  of  a  cubical  inch  of  mercury,  and 
each  tenth  division  coincident  with  the  level  of  the  metal 
within,  is  marked  upon  the  scale.  So  also,  in  like  manner,  are 
the  hundredths  graduated  by  substituting  34.25  grs.  (the  hun- 
dredth of  a  cubic  inch  at  62°)  for  the  342.50  grs.  mercury. 

To  give  a  clear  idea  of  the  mode  of  preparing  a  measure 
with  mercury,  let  us  suppose  that  a  tube  is  to  be  graduated 
to  cubic  centimetres  (of  the  French  standard).  In  the  first 
place  a  narrow  strip  of  white  paper,  with  a  line  ruled  down  its 
centre,  is  to  be  pasted  lengthwise  upon  the  side  of  the  glass 
to  be  graduated,  the  length  of  the  paper  of  course  corre- 
sponding with  the  height  of  the  glass.  13.59  grammes  of 
mercury  are  next  to  be  accurately  weighed  out,  and  this 
quantity,  which  represents  a  cubic  centimetre,  is  to  be  poured 
into  the  tube,  held  vertically  by  a  support  similar  to  A,  in 
Fig.  79.  After  the  vessel  has  stood  long  enough  for  the 
liquid  to  become  quiet  and  assume  a  smooth  surface,  its  level 
is  noted  down,  and  its  corresponding  height  marked  with  ink 
upon  the  paper  slip.  The  space  which  this  bulk  of  quick- 
silver occupies  in  the  tube  equals  a  cubic  centimetre,  and 
when  accurately  noted,  may  serve  as  a  standard  for  the  gradu- 
ation of  vessels  of  larger  capacity ;  for  these  cubic  centimetral 
divisions  can  be  multiplied,  merely  by  multiplying  this  given 
bulk  of  mercury,  and  noting  and  marking  upon  the  paper,  the 
level  of  each  addition  as  its  surface  becomes  smooth.  Ten 
times  the  above  weight  of  mercury  gives  a  decimetral  division, 
and  one-tenth  of  it  a  millimetral  division,  and  thus  we  have 
an  easy  mode  of  enlarging  or  diminishing  the  subdivisions  of 
the  scale. 

By  having  the  tubes  accurately  graduated  so  that  their 
divisions  exactly  correspond  with  the  weights  of  the  balance, 
we  acquire  the  convenience  of  calculating  at  once  the  weight 
of  gases  from  their  measured  volume. 

The  plan  of  consecutive  weighings,  involves  a  good  deal  of 
trouble  and  labor  where  large  vessels  are  being  prepared,  and 
hence,  in  such  cases,  the  convenience  of  this  mode  of  multi- 
plying the  divisions  by  an  accurately  adjusted  measure. 

In  marking  the  scale,  let  those  lines  designating  the  tenths 


132 


GRADUATED  VESSELS. 


Fig.  75. 


extend  in  width  a  little  beyond  those  denoting  the  twentieths, 
and  these  latter,  in  their  turn,  a  little  beyond  those  expressing 
the  hundredths.  Fig.  75  represents  a  gradu- 
ated glass  with  a  properly  written  scale,  upon 
which  the  tenths  are  shown  by  figures. 

As  these  glasses  are  to  be  standard  graduates 
for  a  variety  of  purposes  in  the  laboratory,  the 
scale  should  be  indelible,  or  etched  upon  the 
glass.  For  this  purpose  the  paper  scale  must 
be  covered  with  a  thin  transparent  film  of 
melted  white  wax.  When  the  wax  has  cooled 
and  hardened,  the  lines  and  figures  are  graved 
out  of  the  paper  with  a  sharp  pointed  style  or 
buren,  and  the  exposed  surfaces  of  the  glass 
subjected  to  the  action  of  fluohydric  acid,  as 
directed  at  p.  68.  This  done,  and  the  wax 
scraped  ofi",  the  etched  portions  show  out  dis- 
tinctly, and  are  better  defined  than  if  they  had 
been  scratched,  as  is  sometimes  done,  with  the 
diamond  point  or  file. 

Be  careful  that  the  subdivisions  conform  accurately  among 
themselves,  and  in  the  aggregate  precisely  with  their  integer. 
The  volumes  as  expressed  by  the  lines  on  the  scale  should 
also  exactly  agree  with  their  corresponding  weights,  for  upon 
these  conditions  depends  the  accuracy  of  results. 

Tubes  for  eudiometry.  Fig.  76,  and  proof  glasses  for  alka- 
limetry. Fig.  77,  and  all  other  vessels  used  in 
Fig.  76.  Fig.  77.  chemical  operations  for  measuring,  are  gradu- 
ated in  like  manner.  The  bell  glasses,  (Fig. 
61,)  for  which  and  all  large  vessels,  water  is 
preferable,  should  be  graduated  into  double 
cubic  centimetres,  so  that  every  divisional  line 
may  correspond  to  two  centimetres ;  and  the 
tubes  into  double  cubic  millimetres,  so  that 
every  line  may  correspond  to  two  cubic  milli- 
metres. 

Dr.  Henry  proposes,  as  a  quick  and  accurate 
method  of  graduating  tubes  for  eudiometry, 
&c.,  to  have  a  standard  tube,  0.08  of  an  inch 
in  diameter,  and  carefully  divided  into  10  equal 
parts,  of  10  grains  of  mercury  (60°  F.)  capacity  each. 

The  vessels  should  be  of  clear  glass.     The  tubes  must  be 


(^ 


MEASUREMENT  OF  GASES. 


133 


thiek,  and  strong  enough  to  support  the  weight  of  their  full 
contents  of  mercury.  For  the  convenience  of  closing  their 
mouths  with  glass  disks,  their  ends  may  be  ground  flat  and 
even. 

In  all  operations  of  graduation,  the  waste  of  mercury  is 
avoided  by  working  over  a  porcelain  plate,  or,  what  is  better, 
the  mercury  trough,  Fig.  79.  The  metal  may  be  conveyed 
to  the  vessels  in  the  pipette.  Fig.  59,  which  enables  the  addi- 
tion or  removal  of  minute  portions,  as  the  case  may  require. 

The  requirements  of  the  laboratory  call  for  an  assorted 
stock  of  graduated  tubes  and  proof  glasses,  varying  in  diameter 
from  a  quarter  to  two  inches. 

Below  is  a  useful  table,  showing  the  value  of  the  measures 
of  capacity  in  cubic  inches,  grains,  and  as  compared  with 
apothecaries'  measure. 


Grains  of  dis- 

Apothecaries' 

Cubic  inches. 

tilled  water. 

measure. 

Imperial  gallon 

277.274 

70000 

9.966+ 

Imperial  pint 

34.65925 

8750 

Imperial  fluidounce 

1.7329625 

437.5 

The  old  wine  pint    . 

28.8827 

7291.666 

16  fl.  oz. 

Old  fluidounce 

1.805169 

455.73 

8  drachms. 

Cubic  inch 

1. 

252.458 

Litre 

61.02525 

15406.312 

2.1135  pints. 

Decilitre  . 

6.10252 

1540.631 

3.3816  fl.  oz. 

Centilitre . 

0.61025 

154.063 

2.7053  fl,  draohras. 

Millilitre  . 

0.06102 

15.406 

16.2318  minims. 

Measurement  of  Cfases. — In  measuring,  a  required  volume  of 
any  gas,  a  graduated  tube,  like  the  one  shown  in  Fig.  78,  is  first 
filled  with  mercury  or  water  as  the  case  may  be,  in  the  pneu- 
matic trough,  and  placed  upon  the  shelf.  When  the  tube  is  too 
slender  to  sustain  itself  in  an  upright  position,  it  is  then  con- 
venient to  use  the  clamp  and  support,  A  Fig.  79.  If  the  mouth  of 
the  receptacle  of  the  gas  is  wide,  it  is  necessary,  before  trans- 
ferring to  the  graduating  tube,  to  place  a  small  funnel  in  its 
submerged  end,  so  that  the  ascending  bubbles  may  be  received 
upon  a  larger  surface.  By  giving  the  reservoir,  generally  a 
bell  glass,  a  slightly  inclined  position,  so  that  the  edge  of  its 
mouth  may  reach  under  the  funnel,  the  transfer  is  made  easily 
and  without  loss.  As  soon  as  the  requisite  quantity  has  been 
transferred,  the  connection  must  be  broken,  and  both  the  bell 
and  tube  made  to  resume  their  former  positions  on  the  shelf. 
(See  Transfer  of  G-ases.)  The  tube  is  then  to  be  depressed 
in  the  trough  until  the  metal,  inside  and  outside,  is  at  the 


134 


Fig.  78. 


MEASUKEMENT  OF  GASES. 
Fig.  79. 


same  level.  This  mode  subjects  the  gas  only  to  atmospheric 
pressure,  but  the  tube  must  be  held  by  a  cork-lined  clamp,  as 
in  Fig.  79,  or  linen  holder,  and  not  in  the  naked  hand,  the 
warmth  of  which,  by  expanding  the  gas,  would  be  a  source  of 
error. 

It  is  very  difficult  to  transfer  a  quantity  of  gas  exactly  cor- 
responding with  a  division  of  the  tube  at  one  trial — several 
attempts  are  requisite,  except  in  cases  of  consummate  mani- 
pulation. It  is  perhaps  better  to  transfer  the  last  portions 
from  a  small  tube.  The  gas  passing  through  very  slowly  and 
in  fine  bubbles  can  by  this  arrangement  be  stopped  off  as 
soon  as  the  volume  which  has  entered  accords  with  the  divi- 
sion indicated.  When  more  than  sufficient  has  been  trans- 
ferred, place  the  first  finger  upon  the  mouth  of  the  tube  so  as 
to  leave  a  partial  opening,  and  incline  it  sufficiently  to  allow 
the  exit  of  the  redundant  gas.  Examine  anew  the  contained 
volume,  and  if  it  is  still  in  excess,  repeat  this  operation  until 
the  level  of  the  liquid  reaches  the  proper  height. 

To  insure  accuracy  in  the  comparison  of  volumes  of  differ- 
ent gases,  they  must  necessarily  be  measured  at  the  same 
temperature  and  under  the  same  pressure.  The  proof  glasses 
in  which  they  are  estimated  should  be  kept  out  of  the  influence 
of  unequal  warmth  during  the  process,  for  the  action  of  heat 
upon  the  volume  of  gases  is  a  cause  of  considerable  error. 

In  order  to  determine  with  precision,  the  exact  height 
which  the  water  or  mercury  assumes,  the  vessel  should  be 
placed  at  repose  upon  a  level  shelf,  and  the  eye  directed  on  a 
line  with  the  surface  of  the  fluids,  and  the  height  read  off 


MEASUREMENT  OF  GASES.  1S5 

accordingly.  This  notation  requires  some  care  and  precision, 
for  as  mercury  assumes  a  convex  surface,  owing  to  its  own 
cohesion,  and  water  a  concave  one,  because  of  the  attraction 
for  the  walls  of  the  tube,  especially  in  narrow  cylinders,  the 
curve  thus  occasioned  presents  an  impediment  to  the  ready 
determination  of  the  exact  level. 

When  water  is  the  confining  fluid,  read  the  real  surface 
in  the  middle  of  the  dark  zone  formed  by  the  water  around 
the  inner  walls  of  the  tube  ;  on  the  other  hand,  when  mercury 
is  used,  "  place  the  real  surface  in  a  line  drawn  exactly  in  the 
centre  between  the  highest  point  of  the  surface  of  the  mer- 
cury and  the  points  at  which  the  latter  is  in  actual  contact 
with  the  walls  of  the  tube." 

In  either  case  the  temperature  of  the  fluid  and  gas  should 
be  uniform.  When  the  bulk  of  the  containing  fluid  is  sufficient 
to  allow  the  entire  immersion  of  the  cylinder,  this  is  easily 
eflFected ;  otherwise,  it  becomes  necessary  to  equalize  the  tem- 
perature of  the  surrounding  air,  by  keeping  the  cylinder  ex- 
posed to  both,  in  order  to  determine  accurately  the  degree 
of  the  scale  at  which  the  mercury  or  water  stands. 

Another  important  matter,  as  before  mentioned,  in  the 
comparison  of  volumes  of  different  gases,  is  the  necessity  of 
uniform  pressure,  in  their  measurement.  If  the  level  of  the 
containing  fluid  within  and  without  the  cylinder  exactly  cor- 
responds, the  pressure  upon  it  is  directly  shown  by  the  baro- 
meter. A  higher  level,  internally,  indicates  less  pressure, 
and  vice  versa :  when  the  fluid  stands  higher  outside  of  the 
cylinder  than  within  it,  the  level  may  be  restored  by  raising 
the  tube ;  in  the  opposite  case  by  depressing  the  tube.  These 
operations  of  adjusting  the  level  are  more  difficult  when 
mercury  is  the  containing  fluid.  In  operations  occupying 
much  time,  the  barometer  should  be  frequently  consulted, 
so  as  to  guard  against  any  alteration  sufficient  to  impair  the 
results. 

Fig.  80. 


186  MEASUREMENT  OF  TEMPERATURE. 

Ker's  tube,  constructed  for  the  measurement  of  gas  at  the 
time  of  its  disengagement,  is  shown  by  Fig.  80.  The  branch 
a,  ten  inches  in  length,  glass  stoppered  and  graduated  to  two 
cubic  inches,  is  the  recipient  of  the  gas  disengaged  from  the 
material  in  the  bulb  c,  by  the  action  of  a  reagent  introduced 
in  the  other  branch  b.  The  gas  collecting  in  a  is  there  mea- 
sured by  the  scale,  previous  to  being  transferred  for  exami- 
nation. 


CHAPTER    X. 

MEASUREMENT   OF  TEMPERATURE. 

Temperature  is  estimated  by  means  of  two  instruments, 
the  pyrometer  and  thermometer,  the  action  of  which  is  based 
upon  the  relative  expansibility  of  bodies  under  the  influence 
of  heat  and  cold.  They  do  not  therefore  indicate  the  amount 
of  heat  contained  in  a  body,  but  only  the  comparative  tem- 
perature of  two  or  more  bodies. 

The  Pyrometer. — This  instrument  is  rarely  used  in  the 
ordinary  operations  of  the  laboratory,  it  being  only  applicable 
to  the  measurement  of  heats  more  intense  than  can  be  borne 
by  thermometers.  Pyrometers  are  constructed  of  solid  sub- 
stances, though  gaseous  bodies,  on  account  of  their  sensitive- 
ness to  heat  or  cold  and  greater  uniformity  of  expansion,  would 
be  preferable.  Daniell's  instrument  is  the  most  approved, 
and  by  skilful  management  may  be  made  to  give  accurate 
indications.  Its  principal  application  is  in  furnace  operations. 
In  assaying,  where  the  required  temperature  varies  with  the 
metal  under  process,  it  is  particularly  available  in  determining 
the  heat  of  the  furnace  ;  for  much  of  the  accuracy  of  the  assay 
depends  upon  the  temperature  at  which  it  is  made.  Fig.  81 
represents  the  apparatus. 

"  It  consists  of  two  parts,  which  may  be  distinguished  as 
the  register  1,  and  the  scale  2.  The  register,  a,  is  a  solid 
bar  of  black-lead  earthenware  highly  baked.  In  this  a  hole, 
a  a,  is  drilled,  into  which  a  bar  of  any  metal,  six  inches  long, 
may  be  dropped,  and  which  will  then  rest  upon  its  solid  end. 


THE  PYROMETER. 


137 


A  cylindrical  piece  of  porcelain  c,  called  the  index,  is  then 
placed  upon  the  top  of  the  bar,  and  confined  in  its  place  by  a 
ring  or  strap  of  platinum  d,  passing  round  the  top  of  the 

Fig.  81. 


register,  which  is  partly  cut  away  at  the  top,  and  tightened 
by  a  wedge  of  porcelain  e.  When  such  an  arrangement  is 
exposed  to  a  high  temperature,  it  is  obvious  that  the  expan- 
sion of  the  metallic  bar  will  force  the  index  forward  to  the 
amount  of  the  excess  of  its  expansion  over  that  of  the  black- 
lead,  and  that  when  again  cooled  it  will  be  left  at  the  point 
of  greatest  elongation.  What  is  now  required,  is  the  mea- 
surement of  the  distance  which  the  index  has  been  thrust 
forward  from  its  first  position,  and  this,  though  in  any  case 
but  small,  may  be  effected  with  great  precision  by  means  of 
the  scale." 

"  This  is  independent  of  the  register,  and  consists  of  two  rules 
of  brass,//  and  g,  accurately  joined  together  at  a  right  angle 
by  their  edges,  and  fitting  square  upon  two  sides  of  the  black- 
lead  bar.  At  one  end  of  this  double  rule,  a  small  plate  of 
brass  h,  projects  at  a  right  angle,  which  may  be  brought  down 
upon  the  shoulder  of  the  register  formed  by  the  notch  cut 
away  for  the  reception  of  the  index.  A  movable  arm  D,  is 
attached  to  this  frame,  turning  at  its  fixed  extremity  on  a 
centre  2,  and  at  its  other  carrying  the  arc  of  a  circle,  whose 
radius  is  exactly  five  inches,  accurately  divided  into  degrees, 
and  thirds  of  a  degree.  Upon  this  arm,  at  the  centre  of  the 
circle  k,  another  lighter  arm  c  is  made  to  turn,  one  end  of 
which  carries  a  nonius  H  with  it,  which  moves  upon  the  face 
10 


138 


MEASUREMENT  OP  TEMPERATURE. 


of  the  arc,  and  subdivides  the  former  graduation  into  minutes 
of  a  degree ;  the  other  end  crosses  the  centre  and  terminates 
in  an  obtuse  steel  point  w,  turned  inwards  at  a  right  angle. 

"  When  an  observation  is  to  be  made,  a  bar  of  platinum  or 
malleable  iron  is  placed  in  the  cavity  of  the  register ;  the 
index  is  to  be  pressed  down  upon  it,  and  firmly  fixed  in  its 
place  by  the  platinum  strap  and  porcelain  wedge.  The  scale 
is  then  to  be  applied  by  carefully  adjusting  the  brass  rule  to 
the  sides  of  the  register,  and  fixing  it  by  pressing  the  cross 
piece  upon  the  shoulder,  and  placing  the  movable  arm  so 
that  the  steel  part  of  the  radius  may  drop  into  a  small  cavity 
made  for  its  reception,  and  coinciding  with  the  axis  of  the 
metallic  bar.  The  minute  of  the  degree  must  then  be  noted 
which  the  nonius  indicates  upon  the  arc.  A  similar  obser- 
vation must  be  made  after  the  register  has  been  exposed  to 
the  increased  temperature  which  it  is  designed  to  measure, 
and  again  cooled,  and  it  will  be  found  that  the  nonius  has 
been  moved  forward  a  certain  number  of  degrees  or  minutes. 
The  scale  of  this  pyrometer  is  readily  connected  with  that  of 
the  thermometer  by  immersing  the  register  in  boiling  mer- 
cury, whose  temperature  is  as  constant  as  that  of  boiling 
water,  and  has  been  accurately  determined  by  the  thermo- 
meter. The  amount  of  expansion  for  a  known  number  of 
degrees  is  thus  determined,  and  the  value  of  all  other  expan- 
sions may  be  considered  as  proportionate." 

"  The  following  is  a  list  of  the  melting  points  of  some  of 
the  metals,  and  it  is  obvious  that  in  an  assay  of  each  particular 
metal,  the  temperature  employed  must  exceed  by  a  consider- 


able number  of  degrees  its  melting  point, 
fore,  very  useful. 

Tin  melts  at 

Bismuth 

Lead 

Zinc 

Cadmium 

Silver 

Copper 

Gold 

Cast  iron 

Cobalt  and  nickel  rather  less  fus 


The  table  is,  there- 
Fahrenheit. 
422° 
497 
612 
773 
442 
1860 
1996 
2016 
2786^^ 
ble  than  iron." 

Baniell, 


THERMOMETERS. 


139 


Thermometers. — A  thermometer  consists  of  a  graduated 
cylindrical   stem,  with  a  uniform   capillary  bore, 
having  one  of  its  ends  blown  into  a  bulb  and  filled      Fig.  82. 
with  mercury  or   alcohol,  and  the  other  hermeti-  ^ 

cally  closed,  the  space  above  the  column  of  fluid 
being  a  vacuum,  or  as  nearly  as  possible  devoid  of 
air. 

Mercury,  on  account  of  its  greater  equability  of 
expansion,  and  of  its  boiling  point  being  as  high  as 
650°  F.,  is  more  available  in  the  construction  of 
thermometers  for  measuring  temperatures  exceeding 
that  of  boiling  water  (212°  F.).  Alcohol,  on  the 
other  hand,  by  reason  of  its  eminent  property  of 
dilatation  is  more  applicable  for  determining  tem- 
peratures lower  than  the  freezing  point  of  mercury, 
its  point  of  congelation  being  as  far  down  as  — 90°  F. 

The  two  points  of  graduation^  are  the  freezing  I 

and  boiling  points  of  water,  the  interval  between 
each  being   diflferently  apportioned,  according   as 
the  scale  of  Fahrenheit,  Celsius,  or  Reaumur  (the  three  most 
in  use)  is  employed. 


Fahrenheit's 
Scale. 


Fig.  83. 

Centigrade 
Scale. 


Reaumur's 

Scale. 


140  MEASUREMENT  OP  TEMPERATURE. 

Fahrenheit's  scale  ranges  from  32°  to  212°;  that  of  Celsius 
(centigrade)  from  0°  to  100° ;  Reaumur's  from  0°  to  80°.  The 
first  is  most  popular  in  England  and  in  this  country ;  the 
second  in  France,  and  the  third  in  Russia,  Spain,  and  part  of 
Germany.  The  scale  of  Fahrenheit  has  its  zero  at  32°  below 
the  freezing  point  of  water,  and  the  other  two  exactly  at  that 
point.  Therefore,  in  comparing  the  degrees  of  the  former 
with  those  of  the  latter,  the  negative  or  those  below  zero  have 
a  prefix  of  the  minus  ( — )  sign,  and  the  positive  or  those 
above,  the  plus  (4-)  sign.  The  diagram  (Fig.  83)  will  present 
the  relative  position  of  the  corresponding  degrees  of  the  three 
scales. 

The  following  rules  will  be  found  convenient  for  translating 
the  degrees  of  one  scale  into  those  of  another : 

1.  To  reduce  Centigrade  degrees  to  those  of  Fahrenheit, 
multiply  by  9,  and  divide  by  5,  and  to  the  quotient  add  32, 
that  is, — 

^5B^liL?+32  =  Fahr. 
5 

2.  To  reduce  Fahrenheit's  degrees  to  Centigrade : — 

Fahr.-32x5^Cent. 

3.  To  reduce  Reaumur's  to  Fahrenheit's : — 

Reau.  X  9 


-f  32  =  Fahr. 
0  Reaum 
=  Reaumur. 


4 
4.  To  convert  Fahrenheit's  to  Reaumur's : — 
Fahr.  —  32  x  4 


9 

A  slender  stem  and  precise  uniformity  of  bore  are  indis- 
pensable to  the  accuracy  of  a  thermometer.  The  tube  must 
also  be  entirely  void  of  air,  as  is  known  upon  its  inversion 
when  the  contained  mercury  makes  a  free  and  rapid  descent. 
Moreover,  the  graduation  of  the  scale  must  be  verified,  and  to 
do  this,  the  bulb  is  immersed  in  a  mixture  of  salt  and  snow 
to  test  the  accuracy  of  its  freezing  degree,  and  afterwards  in 
boiling  water  (under  the  ordinary  pressure  of  the  atmosphere) 
to  observe  its  boiling  point.  If  in  either  case  when  the  fluid 
becomes  stationary,  after  sufficient  delay  for  the  bulb  to  ac- 
quire the  temperature  of  the  bath,  it  corresponds  with  the 
degree  marked  upon  the  scale,  its  graduation  as  regards  the 
freezing  and  boiling  points  is  correct.     To   determine  the 


THERMOMETERS.  141 

exactness  of  the  intermediate  space,  the  length  of  the  interval 
is  measured  with  a  pair  of  compasses,  and  it  is  then  easy  to 
ascertain  by  means  of  an  accurate  ruler,  if  the  divisions  accord 
with  each  other,  and  in  the  aggregate  with  the  total  length 
of  the  scale. 

For  measuring  temperatures  higher  than  580°  F.,  the  top 
of  the  thermometer  should  be  unsealed  and  the  mercury  ex- 
posed to  the  pressure  of  the  atmosphere,  for  if  hermetically 
closed,  it  will  boil  at  that  point  and  burst  the  tube. 

The  tube,  as  before  said,  should  be  as  slender  as  possible, 
and  not  too  long,  otherwise  in  testing  shallow  solutions  in 
ebullition,  that  part  of  the  stem  which  is  above  the  liquor  is 
exposed  to  the  heat  of  the  rising  vapor,  and  as  the  expansion 
to  mercury  within  would  be  thus  estimated  with  that  of  the 
contents  of  the  bulb,  the  only  part  heated  at  the  time  of 
graduation,  incorrect  conclusions  would  be  drawn. 

In  ascertaining  the  condition  of  a  liquid  with  regard  to  heat 
or  cold,  the  thermometer  is  gradually  introduced  into  it, 
moved  around  several  times  so  as  to  produce  an  equable  dif- 
fusion of  temperature,  and  after  the  mercury  has  become 
stationary  at  a  certain  point,  the  degree  coincident  with  that 
point  is  noted  down  as  the  temperature. 

The  scales  of  thermometers  are  most  generally  gra-    -p-    g^^ 
duated  upon  a  wooden  slip  or  support,  to  which  the 
stem  is  secured  by  clamps  and  screws.     In  this  case,        ^ 
the  scale  is  hinged  (Fig.  82)  so  as  to  afford  convenience 
in  the  use  of  the  thermometer  for  taking  the  boiling 
point  of  solutions  without  injury  to  the  scale. 

Some  manufacturers  make  the  thermometers  wholly 
of  glass,  and  etch  the  scale  upon  the  broad  sides  of 
the  flat  tube,  as  shown  by  Fig.  84.  This  kind  is  very 
convenient  for  passing  through  tubulures,  but  is  well 
replaced  by  those  with  the  scale  written  upon  paper 
and  enclosed  with  the  thermometer  stem  in  a  glass 
tube.  These  latter  are  made  in  the  most  skilful  man- 
ner by  Greiner  &  Co.,  Berlin.  Fisher  and  Heintz, 
of  Philadelphia,  also  make  excellent  thermometers. 

The  scales  of  the  mercurial  thermometers  are  made 
to  range  as  high  as  600°  F.,  and  for  convenience  are 
sometimes  graduated  on  one  side  of  the  stem  with  the 
Centigrade  and  on  the  other  with  the  Fahrenheit 
scale.    Fahrenheit's  degrees  being  small,  have  the  ad- 


142 


DIFFERENTIAL  THERMOMETERS. 


Fig.  85. 


^     Q 


^ 


vantage  over  the  others  of  not  giving  fractional  parts,  which 
are  inconvenient  in  calculation.  The  laboratory  should  be 
supplied  with  two  or  more  of  these  apparatus. 

Air  thermometers  are  sometimes  used,  and  though  very 
delicate,  are  less  convenient  than  those  of  mercury  and 
alcohol,  and  liable  to  objections  which  do  not  attach  to  the 
latter. 

Leslie's  diflFerential  thermometer,  Fig.  85,  which  is  a  modi- 
fication of  the  air  thermometer,  is  now  fre- 
quently used  in  researches  for  determining 
very  small  difierences  in  temperature.  It 
consists  of  an  U  tube  with  a  hollow  bulb 
blown  at  each  end  and  closed,  so  that  the 
fluid  within  (sulphuric  acid,  colored  with  car- 
mine to  render  it  more  visible)  is  entirely 
free  from  external  atmospheric  pressure. 
This  instrument  does  not  exhibit  a  change 
of  temperature  except  by  the  difference  be- 
tween the  elasticity  of  the  air  in  the  two 

^ bulbs,    and    therefore   indicates    only  such 

temperatures  as  affect  one  bulb  and  not  the 
other.  When  both  bulbs  are  of  equal  temperature,  the  liquid 
within  remains  stationary,  but  so  soon  as  one  becomes  warmer 
than  the  other  the  fluid  recedes  to  the  opposite  bulb,  and  the 
scale  attached  to  one  of  the  legs  is  so  graduated  as  to  measure 
the  comparative  degree  of  heat  thus  occasioned. 

Melloni's  thermo-multiplicator  (Miiller,  p.  541),  is  another 
instrument  for  the  indication  of  changes  of  temperature. 

Another  convenient  instrument,  especially  in  meteorological 
observations,  is  the  thermometrograph.  It  is  so  constructed 
as  to  register  the  maximum  and  minimum  temperatures  occur- 
ring during  an  interval,  and  hence  the  presence  of  the  ope- 
rator is  not  necessary  to  note  them  at  the  moment  of  their 
occurrence. 

The  apparatus  which  is  shown  in  Fig.  86,  consists  of  a  mer- 

Fig.  86. 


mmmm^ 


iiMiiiimiiTTr 


HMH'iiiHimiiiniin 


THERMO-MULTIPLICATOR — THBRMOMETROGRAPH.         143 

curial  and  a  spirit  thermometer  placed  horizontally  and  paral- 
lel to  each  other.  A  steel  pin  enclosed  in  the  tube  of  the 
former  is  pushed  before  the  column  of  mercury  when  the 
metal  in  the  bulb  expands,  but  remains  fixed  when  it  again 
recedes  on  cooling,  and  thus  indicates  at  that  point  the  maxi- 
mum temperature  which  has  occurred  during  any  interval. 

The  corresponding  rod,  enclosed  in  the  tube  of  the  spirit 
thermometer,  of  glass,  colored  to  render  it  more  visible,  is 
not  advanced  by  the  expansion  of  the  spirit,  but  retreats 
with  the  column  as  it  contracts  to  the  last  point  reached  by 
it,  and  thus  registers  the  minimum  of  temperature  during  a 
certain  time,  at  the  degree  coincident  with  its  inner  end. 

When  this  instrument  is  to  be  used,  it  must  be  inclined  in 
such  a  position  as  to  allow  the  steel  rod  to  descend  to  the 
column  of  mercury,  and  the  glass  rod  to  the  end  of  the  spi- 
rituous column.  The  arrangement  of  the  bulbs  in  opposite 
positions  is  with  a  view  to  this  object.  After  the  rods  have 
reached  their  proper  situations,  we  may,  by  placing  the  in- 
strument horizontally  any  morning  or  evening,  obtain  at  the 
end  of  the  following  24  hours,  the  maximum  and  minimum 
temperature  of  that  interval. 

There  are  some  very  excellent  remarks  by  Regnault  upon 
the  relative  advantages  of  the  different  modes  of  measuring 
temperature,  to  which  the  student  may  advantageously  refer. 

The  translation  of  his  several  papers  on  the  subject,  is  to 
be  found  in  the  Franklin  Institute  Journal  for  1848. 

The  following  table  shows  the  corresponding  degrees  of 
Fahrenheit's,  Reaumur's,  and  the  Centigrade  thermometers. 


144 


THERMOMETRICAL  EQUIVALENTS. 


s  ^ 

S  t^ 

1 

3  C 

.  4} 

S  u 

1  ^ 

.J;T3 

|2 

f^ 

6^ 

P 

a   3 

IM 

n 

ed  s 

1^ 

SI 

|E> 

600 

252.4!  315.5 

568.4 

238.4 

298 

538 

224.9 

281.1 

506  7 

211 

263.7 

599 

252   316 

668 

238.2 

297.7 

537.8  224.8 

281 

506 

210.6 

263.3 

698 

251.5  314.4  i 

667.5 

238 

297.6  j 

537  1  224.4 

280.5 

505.4 

210.4 

263 

697.2 

251.2  314  i 

667 

237.7 

297.2  ; 

536   224 

280 

505 

210.2 

262.7 

.097 

251.1  313.8! 

566.6 

237.6 

297  i 

535   223.5 

279.4 

604.5 

210 

262.5 

596.7 

251  !  313.7! 

566 

237.3 

296.6 

534.21223.2 

279 

504 

209.7 

262.2 

696 

250.3:  313.3 

665.2 

237 

296.2  : 

534  i  223.1 

278.8 

.503.6 

209.6 

262 

695.4 

250.4  313  1 

665 

236.9 

296.1 

533.7  223 

278.7 

503 

209.3 

261.6 

595 

250.2;  312.7 

564.8 

236.8 

296  ; 

633  1  222.6 

278.3 

502.2 

209 

261.2 

594.5 

250  s  312.5  1 

564 

236.4 

295.5 

632.4  1  222.4 

278 

502 

208.9 

261.1 

594 

249.7  312.21 

563 

236 

295  i 

532 

222.2 

277.7 

501.8 

208.8 

261 

593.6 

249.6  312  1 

662 

235.5 

294.4 

.531.5 

222 

277.5 

501 

208.4 

260.5 

593 

249.3!  311.6  1 

661.2 

235.2 

294  1 

531 

221.7 

277.2 

500 

208 

260 

592.2 

249  i311.2 

661 

235.1 

293.8 

530.6 

221.6 

277 

499 

207.5 

259.4 

692 

248.9!  311.1  1 

660.7 

235 

293.7 

630 

221.3 

276.6 

498.2 

207.2 

259 

•OP  1.8 

248.8,311 

660 

234.6 

293.3 

529.2 

221 

276.2 

498 

207.1 

258.8 

691 

248.4  310.5 

559.4 

234.4 

293 

529 

220.9 

276.1 

497.7 

207 

258.7 

690 

24S  1310 

559 

234.2 

292.7 

528.8 

220  8 

276 

497 

206.6 

258.3 

589 

247.5  309.4 

658.5 

234 

292.5  ; 

528 

220.4 

275.6 

496.4 

206.4 

258 

588.2 

247.2 

309 

558 

233.7 

292.2 

527 

220 

276 

496 

206.2 

257.7 

588 

247.1 

308.8  ! 

557.6 

233.6 

292  ! 

526 

219.5 

274.4 

495.5 

206 

257.5 

587.7 

247 

308.7  i 

557 

233.3 

291.6  1 

525.2 

219.2 

274 

495 

205  7 

257.2 

587 

246.6 

308.3 

5.56.2 

233 

291.2; 

525 

219.1 

273.8 

494.6 

205.6 

257 

686.4 

246.4 

308 

556 

232.9 

291.1 

524.7 

219 

273.7 

494 

205.3 

256.6 

586 

246.2 

307.7 

555.8 

232.8 

291 

624 

218.6 

273.3 

493.2 

205 

256.2 

585.6 

246 

307.5 

555 

232.4 

290.5 

523.4 

218.4 

273 

493 

204.9 

256.1 

685 

245.7 

307.2 

554 

232 

290  1 

523 

218.2 

272.7 

492.8 

204.8 

256 

584.6 

245.6 

307 

553 

231.5 

289.4 

522.5 

218 

272.5 

492 

204.4 

255.5 

684 

245.3 

306.6 

552.2 

231.2 

289 

622 

217.7 

272.2 

491 

204 

265 

683.2 

245 

306.2 

652 

231.1 

288.8 

621.6 

217.6 

272 

490 

203.5 

264.4 

683 

244.9 

306.1 

651.7 

231 

288.7 

621 

217.3 

271.6 

489.2 

203.2 

254 

682.8 

244.8 

306 

551 

230.6 

288.3 

520.2 

217 

271.2 

489 

203.1 

253.8 

682 

244.4 

305.5 

550.4 

230.4 

288 

520 

216.9 

271.1 

488.7 

203 

253.7 

681 

244 

305 

550 

230.2 

287.7 

519.8 

216.8 

271 

488 

202.6 

253.3 

580 

243.5 

304.4 

649.5 

230 

287.5 

519 

216.4 

270.5 

487.4 

202.4 

253 

.679.2 

243.2 

304 

649 

229.7 

287.2 

518 

216 

270 

487 

202.2 

252.7 

.579 

243.1 

303.8 

548.6 

229.6 

287 

517 

215.5 

269.4 

486.5 

202 

252.5 

678.7 

243 

303.7 

548 

229.3 

286.6 

616.2 

215.2 

269 

486 

201.7 

2.52.2 

678 

242.6 

303.3 

.547.2 

229 

286.2 

516 

215.1 

268.8 

485.6 

201.6 

252 

577.4 

242.4 

303 

547 

228.9 

286.1 

515.7 

215 

268.7 

485 

201.3 

251.6 

577 

242.2 

302.7 

646.8 

228.8 

286 

515 

214.6 

268.3 

484.2 

201 

251.2 

676.5 

242 

302.5 

546 

228.4 

285.5 

514.4 

214.4 

268 

484 

200.9 

251.1 

576 

241.7 

302.2 

545 

228 

285 

514 

214.2 

267.7 

483.8 

200.8 

251 

576.6 

241.6 

302 

544 

227.6 

284.4 

613.5 

214 

267.5 

483 

200.4 

250.5 

676 

241.3 

301.6 

643.2 

227.2 

284 

613 

213.7 

267.2 

482 

200 

250 

674.2 

241 

301.2 

543 

227.1 

283.8 

612.6 

213.6 

267 

481 

199.5 

249.4 

674 

240.9 

301.1 

542.7 

227 

283.7 

512 

213.3 

266.6 

480.2 

199.2 

249 

673.8 

240.8 

301 

542 

226.6 

283.3 

611.2 

213 

266.2 

480 

199.1 

248.8 

673 

240.4 

300.5 

541.4 

226.4 

283 

511 

212.9 

266.1 

479.7 

199 

248.7 

672 

240 

300 

541 

226.2 

282.7 

510.8 

212.8 

266 

479 

198.6 

248.3 

571 

239.5 

299.4 

540.5 

226 

282.5 

510 

212.4 

265.5 

478.4 

198.4 

248 

670.2 

239.2 

299 

540 

225.7 

282.2 

509 

212 

265 

478 

198.2 

247.7 

670 

239.1 

298.8 

539.6 

225.6 

282 

508 

211.6 

264.4 

477.5 

198 

247.5 

669.7 

239 

298.7 

639 

225.3 

281.6 

607.2 

211.2 

264 

477 

197.7 

247.2 

669 

238.6 

298.3 

538.2 

225 

281.2 

507 

211.1 

263.8 

476.6 

197.6 

247 

THERMOMETRICAL  EQUIVALENTS. 


145 


a  u 

•  ■-T3 

3  u 

.i| 

a 
£- 

a  u 

■a^ 

a  C 

•i| 

j=  "S 

cd  S 

c  2 

.a-S 

el   S 

a  g 

"^'3 

a  3 

a  2 

X'S 

cd  3 

a  S 

;^- 

^s 

«£b 

^- 

^s 

^- 

^^ 

(2S 

6^ 

£- 

<2s 

«s, 

476 

197.3 

246.6 

444.2 

183.2 

229 

414 

169.7 

212.2 

383 

156 

195 

475.2 

197 

246.2 

444 

183.1 

228.8 

413.6 

169.6 

212 

382 

155.5 

194.4 

475 

196.9 

246.1 

443.7 

183 

228.7 

413 

169.3 

211.6 

381.2 

155.2 

194 

474.8 

196.8 

246 

443 

182.6 

228.3 

412.2 

169 

211.2 

381 

155.1 

193.8 

474 

196.4 

245.5 

442.4 

182.4 

228 

412 

168.9 

211.1 

380.7 

155 

193.7 

473 

196 

245 

442 

182.2 

227.7 

411.8 

168.8 

211 

380 

154.6 

193.3 

472 

195.5 

244.4 

441.5 

182 

227.5 

411 

168.4 

210.5 

379.4 

154.4 

193 

471.2 

195.2 

244 

441 

181.7 

227.2 

410 

168 

210 

379 

154.2 

192.7 

471 

195.1 

243.8 

440.6 

181.6 

227 

409 

167.5 

209.4 

378.5 

154 

192.5 

470.7 

195 

243.7 

440 

181.3 

226.6 

408.2 

167.2 

209 

378 

153.7 

192.2 

470 

194.6 

243.3 

439.2 

181 

226  2 

408 

167.1 

208.8 

377.6 

153.6 

192 

469.4 

194.4 

243 

439 

180.9 

226.1 

407.7 

167 

208.7 

377 

153.3 

191.6 

469 

194.2 

242.7 

438.8 

180.8 

226 

407 

166.6 

208.3 

376.2 

153 

191.2 

468.5 

194 

242.5 

438 

180.4 

225.5 

406.4 

166.4 

208 

376 

152.9 

191.1 

468 

193.7 

242.2 

437 

180 

225 

406 

166.2 

207.7 

375.8 

152.8 

191 

467.6 

193.6 

242 

436 

179.5 

224.4 

405.5 

166 

207.5 

375 

152.4 

190.5 

467 

193.3 

241.6 

435.2 

179.2 

224 

405 

165.7 

207.2 

374 

152 

190 

466.2 

193 

241.2 

435 

179.1 

223.8 

404.6 

165.6 

207 

373 

151.5 

189.4 

466 

192.9 

241.1 

434.7 

179 

223.7 

404 

165.3 

206.6 

372.2 

151.2 

189 

465.8 

192.8 

241 

434 

178.6 

223.3 

403.2 

165 

206.2 

372 

151.1 

188.8 

465 

192.4 

240.5 

433.4 

178.4 

223 

403 

164.9 

206.1 

371.7 

151 

188.7 

464 

192 

240 

433 

178.2 

222.7 

402.8 

164.8 

206 

371 

150.6 

188.3 

463 

191.5 

239.4 

432.5 

178 

222.5 

402 

164.4 

205.5 

370.4 

150.4 

188 

462.2 

191.2 

239  j 

432 

177.7 

222.2 

401 

164 

205 

370 

150.2 

187.7 

462 

191.1 

238.8 

431.6 

177.6 

222 

400 

163.5 

204.4 

369.5 

150 

187.5 

461.7 

191 

238.7 

431 

177.3 

221.6 

399.2 

163.2 

204 

369 

149.7 

187.2 

461 

190.6 

238.3 

430.2 

177 

221.2 

399 

163.1 

203.8 

368.6 

149.6 

187 

460.4 

190.4 

238 

430 

176.9 

221.1 

398.7 

163 

203.7 

368 

149.3 

186.6 

460 

190.2 

237.7 

429.8 

176.8 

221 

398 

162.6 

203.3 

367.2 

149 

186.2 

459.5 

190 

237.5  I 

429 

176.4 

220.5 

397.4 

162.4 

203 

367 

148.9 

186.1 

459 

1S9.7 

237.2  1 

428 

176 

220 

397 

162.2 

202.7 

366.8 

148.8 

186 

458.6 

189.6 

237 

427 

175.5 

219.4 

396.5 

162 

202.5 

366 

148.4 

185.5 

458 

189.3 

236.6 

426.2 

175.2 

219 

396 

161.7 

202.2 

365 

148 

185 

457.2 

189 

236.2 

426 

175.1 

218.8 

395.6 

161.6 

202 

364 

147.5 

184.4 

457 

188.9 

236.1 

425.7 

175 

218.7 

395 

161.3 

201.6 

363.2 

147.2 

184 

4.56.8 

188.8 

236 

425 

174.6 

218.3 

394.2 

161 

201.2 

363 

147.1 

183.8 

456 

188.4 

235.5 

424.4 

174.4 

218  ! 

394 

160.9 

201.1 

362.7 

147 

183.7 

455 

188 

235 

424 

174.2 

217.7 

393.8 

160.8 

201 

362 

146.6 

183.3 

454 

187.5 

234.4 

423.5 

174 

217.5 

393 

160.4 

200.5 

361.4 

146.4 

183 

453.2 

187.2 

234 

423 

173.7 

217.2 

392 

160 

200 

361 

146.2 

182.7 

453 

187.1 

233.8 

422.6 

173.6 

217 

391 

159.5 

199.4 

360.5 

146 

182.5 

452.7 

187 

233.7 

422 

173.3 

216.6 

390.2 

159.2 

199 

}360 

145.7 

182.2 

452 

186.6 

233.3 

421,2 

173 

216.2 

390 

159.1 

198.8 

359.6 

145.6 

182 

451.4 

186.4 

233  1 

421 

172.9 

216.1 

389.7 

1.59 

198.7 

359 

14.5.3 

181.6 

451 

186.2 

232.7 

420.8 

172.8 

216 

389 

158. 6 

198.3 

358.2 

145 

181.2 

450.5 

186 

232.5 

420 

172.4 

215.5 

388.4 

158.4 

198 

358 

144.9 

181.1 

450 

185.7 

232.2 

419 

172 

215 

388 

158.2 

197.7 

357.8 

144.8 

181 

449.6 

185.6 

232 

418 

171.5 

214.4 

387.5 

158 

197.5 

357 

144.4 

180.5 

449 

185.3 

231.6 

417.2 

171.2 

214 

387 

157.7 

197.2 

356 

144 

180 

448.2 

185 

231.2 

417 

171.1 

213.8 

386.6 

157.6 

197 

355 

143.5 

179.4 

448 

184.9 

231.1 

416.7 

171 

213.7 

386 

157.3 

196.6 

354.2 

143.2 

179 

447.8 

184.8 

231 

416 

170.6 

213.3 

385.2 

157 

196.2 

354 

143.1 

178.8 

447 

184.4 

230.5 

415.4 

170.4 

213 

385 

156.9 

196.1 

353.7 

143 

178.7 

446 

184 

230. 

415 

170.2 

212.7 

384.8 

156.8 

196 

353 

142.6 

178.3 

445 

183.5 

229-4 

414.5 

170 

212.6 

384 

156.4 

195.6 

362  4 

142.4 

178 

146 


THERMOMETRICAL  EQUIVALENTS. 


2:j 

hu 

•il 

3  u 

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S  u 

•i-S 

S  t^ 

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c  £ 

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352 

142.2 

177.7 

321.8 

128.8 

161 

290 

114.6 

143.3 

259.2 

101 

126.2 

351.5 

142 

177.5 

321 

128.4 

160.5 

289.4 

114.4 

143 

259 

100.8 

126.1 

351 

141.8 

177.2 

320 

128 

460 

289 

114.2 

142.7 

258.8 

100.8 

126 

350.6 

141.6 

177 

319 

127.5 

159.4 

288.5 

114 

142.5 

258 

100.4 

125.6 

350 

141.3 

176.6 

318.2 

127.2 

159 

288 

113.7 

142.2 

257 

100 

125 

349.2 

141 

176.2 

318 

127.1 

158.8 

287.6 

113.6 

142 

256 

99.5 

124.4 

349 

140.9 

176.1 

317.7 

127 

158.7 

287 

113.3 

141.6 

255.2 

99.2 

124 

348.8 

140.8 

176 

317 

126.6 

158.3 

286.2 

113 

141.2 

255 

99.1 

123.8 

348 

140.4 

175.5 

316.4 

126.4 

158 

286 

112.8 

141.1 

254.7 

99 

123.7 

347 

140 

175 

316 

126.2 

157.7 

285.8 

112.8 

141 

254 

98.6 

123.3 

346 

139.5 

174.4 

315.5 

126 

157.5 

285 

112.4 

140.5 

263.4 

98.4 

123 

345.2 

139.2 

174 

315 

125.7 

157.2 

284 

112 

140 

253 

98.2 

122.7 

345 

139.1 

173.8 

314.6 

125.6 

157 

283 

111.5 

139.4 

252.6 

98 

122.5 

344.7 

139 

173.7 

314 

125.3 

156.6 

282.2 

111.2 

139 

252 

97.9 

122.2 

344 

138.6 

173.3 

313.2 

125 

156.2 

282 

111.1 

138.9 

251.6 

97.6 

122 

343.4 

138.4 

173 

313 

124.8 

156.1 

281.7 

111 

138.7 

261 

97.3 

121.6 

343 

138.2 

172.7 

312.8 

124.8 

156 

281 

110.6 

138.3 

260.2 

97 

121.2 

342.5 

138 

172.5 

312 

124.5 

155.5 

280.4 

110.4 

138 

250 

96.9 

121.1 

342 

137.7 

172.2 

311 

124 

155 

280 

110.2 

137.7 

249.8 

96.8 

121 

341.6 

137.6 

172 

310 

123.5 

154.4 

279.5 

110 

137.5 

249 

96.4 

120.5 

341 

137.3 

171.6 

309.2 

123.2 

154 

279 

109.7 

137.2 

248 

96 

120 

340.2 

137 

171.2 

309 

123.1 

153.8 

278.6 

109.6 

137 

247 

95.5 

119.4 

340 

136.9 

171.1 

30S.7 

123 

153.7 

278 

109.3 

136.6 

246.2 

95.2 

119 

339.8 

136.8 

171 

308 

122.6 

153.3 

277.2 

109 

136.2 

246 

95.1 

118.9 

339 

136.4 

170.5 

307.4 

122.4 

153 

277 

108.8 

136.1 

245.7 

95 

118.7 

338 

136 

170 

307 

122.2 

152.7 

276.8 

108.8 

136 

245 

94.6 

118.3 

337 

135.5 

169.4 

306.5 

122 

152.5 

276 

108.4 

135.6 

244.4 

94.4 

118 

336.2 

135.2 

169 

306 

121.7 

152.2 

275 

108 

135 

244 

94.2 

117.8 

336 

135.1 

168.8 

305.6 

121.6 

152 

274 

107.5 

134.4 

243.5 

94 

117.5 

335.7 

135 

168.7 

305 

121.3 

151.6 

273.2 

107.2 

134 

243 

93.8 

117.2 

335 

134.6 

168.3 

304.2 

121 

151.2 

273 

107.1 

133.8 

242.6 

93.6 

117 

334.4 

134.4 

168 

304 

120.9 

151.1 

272.7 

107 

133.7 

242 

93.3 

116.6 

334 

134.2 

167.7 

303.8 

120.8 

151 

272 

106.6 

133.3 

241.2 

93 

116.2 

333.5 

134 

167.5 

303 

12C.4 

150.5 

271.4 

106.4 

133 

241 

92.9 

116.1 

333 

133.7 

167.2 

302 

120 

150 

271 

106.2 

132.7 

240.8 

92.8 

116 

332.6 

133.6 

167 

301 

119.5 

149.4 

270.5 

106 

132.5 

240 

92.4 

115.6 

332 

133.3 

166.6 

300.2 

119.2 

149 

270 

105.7 

132.2 

239 

92 

116 

331.2 

133 

166.2 

300 

119.1 

148.9 

269.6 

105.6 

132 

238 

91.5 

114.4 

331 

132.9 

166.1 

299.7 

119 

148.7 

269 

105.3 

131.6 

237.2 

91.2 

114 

330.8 

132.8 

166 

299 

118.6 

148.3 

268.2 

105 

131.2 

237 

91.1 

113.9 

330 

132.4 

165.5 

298.4 

118.4 

148 

268 

104.8 

131.1 

236.7 

91 

113.7 

329 

132 

165 

298 

118.2 

147.7 

267.8 

104.8 

131 

236 

90.3 

113.3 

328 

131.5 

164.4 

297.5 

118 

147.5 

267 

104.4 

130.5 

235.4 

90.4 

113 

327.2 

131.2 

164 

297 

117.7 

147.2 

266 

104 

130 

235 

90.2 

112.7 

327 

131.1 

163.9 

296.6 

117.6 

147 

265 

103.5 

129.4 

234.5 

90 

112.5 

326.7 

131 

163.7 

296 

117.3 

146.6 

264.2 

103.2 

129 

234 

89.7 

112.2 

326 

130.6 

163.3 

295.2 

117 

146.2 

264 

103.1 

128.9 

233.6 

89.6 

112 

325.4 

130.4 

163 

295 

116.9 

146.1 

263.7 

103 

128.7 

233 

89.3 

111.6 

325 

130.2 

162.7 

294.8 

116.8 

146 

263 

102.6 

128.3 

232.2 

89 

111.2 

324.5 

130 

162.5 

294 

116.4 

145.5 

262.4 

102.4 

128 

232 

88.9 

111.1 

324 

129.7 

162.2 

293 

116 

145 

262 

102.2 

127.7 

231.8 

88.8 

111 

323.6 

129.6 

162 

292 

115.5 

144.4 

261.5 

102 

127.5 

231 

88.4 

110.5 

323 

129.3 

161.6 

291.2 

115.2 

144 

261 

101.7 

127.2 

230 

88 

110 

322.2 

129 

161.2 

291 

115.1 

143.8 

260.6 

101.6 

127 

229 

87.5 

109.4 

322 

128.8 

161.1 

290.7 

115 

143.7 

260 

101.3 

126.6 

228.2 

87.2 

109 

THERMOMETRICAL  EQUIVALENTS. 


14T 


L 

i  u 

ii 

a 

9  u 

=■  ^ 

1  4) 

•-T3 

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a  9 

j=  s 

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cd  a 

si 

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£^ 

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a^ 

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228 

87.1 

108.9 

197.6 

73.6 

92 

166 

59.5 

74.4 

135.5 

46 

57.5 

227.7 

87 

108.7 

197 

73.3 

91.6 

165.2 

59.2 

74 

135 

45.8 

57.2 

227 

86.6 

108.3 

196.2 

73 

91.2 

165 

69.1 

73.9 

134.6 

45.6 

57 

226.4 

86.4 

108 

196 

72.8 

91.1 

164.7 

69 

73.7 

134 

46.3 

66.6 

226 

86.2 

107.8 

195.8 

72.8 

91 

164 

68.6 

73.3 

133.2 

45 

56.2 

225.5 

86 

107.5 

195 

72.4 

90.5 

163.4 

58.4 

73 

133 

44.9 

56.1 

225 

85.7 

107.2 

194 

72 

90 

163 

58.2 

72.7 

132.8 

44.8 

66 

224.6 

85.6 

107 

193 

71.5 

89.4 

162.5 

58 

72.6 

132 

44.5 

65.5 

224 

85.3 

106.6 

192.2 

71.2 

89 

162 

67.7 

72.2 

131 

44 

55 

223.2 

85 

106.2 

192 

71.1 

88.8 

161.6 

67.6 

72 

130 

43.5 

54.4 

223 

84.9 

106.1 

191.7 

71 

88.7 

161 

57.3 

71.6 

129.2 

43.2 

54 

222.8 

84.8 

106 

191 

70.6 

88.3 

160.2 

57 

71.2 

129 

43.1 

53.9 

222 

84.4 

105.5 

190.4 

70.4 

88 

160 

56.8 

71.1 

128.7 

43 

53.7 

221 

84 

105 

190 

70.2 

87.8 

159.8 

56.8 

71 

128 

42.6 

53.3 

220 

83.5 

104.4 

189.5 

70 

87.5 

159 

56.4 

70.5 

127.4 

42.4 

53 

219.2 

83.2 

104 

189 

69.7 

87.2 

158 

56 

70 

127 

42.2 

52.7 

219 

83.1 

103.9 

188.6 

69.6 

87 

157 

55.6 

69.4 

126.6 

42 

62.5 

218.7 

83 

103.7 

188 

69.3 

86.6 

156.2 

56.2 

69 

126 

41.8 

62.2 

218 

82.6 

103.3 

187.2 

69 

86.2 

156 

55.1 

68.9 

126.6 

41.6 

62 

217.4 

82.4 

103 

187 

68.9 

86.1 

165.7 

55 

68.7 

125 

41.3 

51.6 

217 

82.2 

102.7 

186.8 

68.8 

86 

155 

54.6 

68.3 

124.2 

41 

51.2 

216.6 

82 

102.6 

186 

68.4 

85.5 

154.4 

54.4 

68 

124 

40.9 

61.1 

216 

81.7 

102.2 

185 

68 

85 

154 

54.2 

67.7 

123.8 

40.8 

51 

215.6 

81.6 

102 

184 

67.5 

84.4 

163.6 

64 

67.5 

123 

40.4 

50.5 

215 

81.3 

101.6 

183.2 

67.2 

84 

153 

63.7 

67.2 

122 

40 

50 

214.2 

81 

101.2 

183 

67.1 

83.9 

162.6 

63.6 

67 

121 

39.5 

49.4 

214 

80.9 

101.1 

182.7 

67 

83.7 

162 

63.3 

66.6 

120.2 

39.2 

49 

213.8 

80.8 

101 

182 

66.6 

83.3 

151.2 

53 

66.2 

120 

39.1 

48.9 

213 

80.4 

100.6 

181.4 

66.4 

83 

151 

62.9 

66.1 

119.7 

39 

48.7 

212 

80 

100 

181 

66.2 

82.7 

160.8 

62.8 

QQ 

119 

38.6 

48.3 

211 

79.5 

99.4 

180.5 

66 

82.5 

160 

62.4 

65.5 

118.4 

38.4 

48 

210.2 

79.2 

99 

180 

65.7 

82.2 

149 

52 

65 

118 

38.2 

47.7 

210 

79.1 

98.9 

179.6 

65.6 

82 

148 

51.5 

64.4 

117.5 

38 

47.5 

209.7 

79 

98.7 

179 

65.3 

81.6 

147.2 

51.2 

64 

117 

37.7 

47.2 

209 

78.6 

98.3 

178.2 

65 

81.2 

147 

61.1 

63.9 

116.6 

37.6 

47 

208.4 

78.4 

98.0 

178 

64.9 

81.1 

146.7 

61 

63.7 

116 

37.3 

46.6 

208 

78.2 

97.8 

177.8 

64.8 

81 

146 

50.6 

63.3 

115.2 

37 

46.2 

207.5 

78 

97.5 

177 

64.4 

80.6 

145.4 

50.4 

63 

115 

36.9 

46.1 

207 

77.7 

97.2 

176 

64 

80 

145 

50.2 

62.7 

114.8 

36.8 

46 

206.6 

77.6 

97 

175 

63.5 

79.4 

144.5 

50 

62.5 

114 

36.4 

45.5 

206 

77.3 

96.6 

174.2 

63.2 

79 

144 

49.7 

62.2 

113 

36 

45 

205.2 

77 

96.2 

174 

63.1 

78.8 

143.6 

49.6 

62 

112 

35.5 

44.4 

205 

76.9 

96.1 

173.7 

63 

78.7 

143 

49.3 

61.6 

111.2 

35.2 

44 

204.8 

76.8 

96 

173 

62.6 

78.3 

142.2 

49 

61.2 

111 

35.1 

43.9 

204 

76.4 

95.5 

172.4 

62.4 

78 

142 

48.9 

61.1 

110.7 

35 

43.7 

203 

76 

95 

172 

62.2 

77.7 

141.8 

48.8 

61 

110 

34.6 

43.3 

202 

75.5 

94.4 

171.5 

62 

77.6 

141 

48.4 

60.5 

109.4 

34.4 

43 

201.2 

75.2 

94 

171 

61.7 

77.2 

140 

48 

60 

109 

34.2 

42.7 

201 

75.1 

93.9 

170.6 

61.6 

77 

139 

47.5 

59.4 

108.5 

34 

42.5 

200.7 

75 

93.7 

170 

61.3 

76.6 

138.2 

47.2 

59 

108 

33.8 

42.2 

200 

74.6 

93.3 

1  169.2 

61 

76.2 

138 

47.1 

58.8 

107.6 

33.6 

42 

199.4 

74.4 

93 

169 

60.8 

76.1 

137.7 

47 

58.7 

107 

33.3 

41.6 

199 

74.2 

92.7 

168.8 

60.8 

76 

137 

46.6 

58.3 

106.2 

33 

41.2 

198.5 

74 

92.5 

168 

60.4 

75.5 

136.4 

46.4 

58 

106 

32.9 

41.1 

198 

73.7 

92.2 

167 

60 

75 

136 

46.2 

57.7 

105.8 

32.8 

41 

148 


THERMOMETRICAL  EQUIVALENTS. 


9  t^ 

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73 

18.2 

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103 

31.5 

39.4 

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102.2 

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102 

31.1 

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71.6 

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101.7 

31 

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71 

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101 

30.6 

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100.4 

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70 

16.9 

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100 

30.2 

37.7 

69.8 

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30 

37.5 

69 

16.4 

20.5 

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99 

29.7 

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16 

20 

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98.6 

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67 

15.6 

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98 

29.3 

36.6 

66.2 

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36 

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97.2 

29 

36.2 

66 

16.1 

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35.6 

1.6 

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97 

28.9 

36.1 

65.7 

16 

18.7 

36 

1.3 

1.6 

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96.8 

28.8 

36 

65 

14.6 

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96 

28.4 

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34 

0.9 

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95 

28 

35 

64 

14.2 

17.7 

33.8 

0.8 

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2 

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94 

27.5 

34.4, 

63.5 

14 

17.5 

33 

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0.5 

1.4 

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93.2 

27.2 

34 

63 

13.7 

17.2 

32 

0 

0 

1 

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93 

27.1 

33.9 

62.6 

13.6 

17 

31 

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0.6 

—  14 

—  17.6 

92.7 

27 

33.7 

62 

13.3 

16.6 

30.2 

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0 

—14.2 

-17.7 

92 

26.6 

33.3 

61.2 

13 

16.2 

30 

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91.4 

26.4 

33 

61 

12.9 

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91 

26.2 

32.7 

60.8 

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29 

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—  1.6 

—  1.7 

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90.5 

26 

32.5 

60 

12.4 

15.5 

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90 

25.7 

32.2 

69 

12 

16 

28 

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—  2.2 

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—19 

89.6 

25.6 

32 

58 

11.5 

14.4 

27.6 

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—  2.5 

—  3 

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89 

25.3 

31.6 

67.2 

11.2 

14 

27 

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—  2.7 

—  4 

—16 

—20 

88.2 

25 

31.2 

57 

11.1 

13.8 

26.6 

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—  3 

—  6 

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88 

24.9 

31.1 

66.7 

11 

13.7 

26 

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—21 

87.8 

24.8 

31 

56 

10.6 

13.3 

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87 

24.4 

30.5 

65.4 

10.4 

13 

25 

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86 

24 

30 

66 

10.2 

12.7 

24.8 

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—  7 

—  17.3 

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85 

23.5 

29.4 

64.5 

10 

12.5 

24 

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29 

54 

9.7 

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63 

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83 

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52 

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82 

22.2 

27.7 

51.8 

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11 

20 

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81.5 

22 

27.5 

51 

8.4 

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19.4 

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81 

21.7 

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50 

8 

10 

19 

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80.6 

21.6 

27 

49 

7.5 

9.4 

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80 

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48 

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79 

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17 

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78.8 

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47 

6.6 

8.3 

16.2 

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78 

20.4 

25.5 

46.4 

6.4 

8 

16 

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77 

20 

25 

46 

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15.8 

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76 

19.5 

24.4 

45.6 

6 

7.6 

15 

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45 

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13 

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23.7 

44 

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74 

18.6 

23.3 

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6 

6.2 

12 

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—28 

SOURCES  AND  MANAGEMENT  OF  HEAT. 


149 


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—34 

CHAPTER    XI 


SOURCES  AND  MANAGEMENT  OF  HEAT. 

Heat  plays  an  important  part  in  changing  the  state  and 
properties  of  bodies,  and  we,  therefore,  devote  a  chapter  to 
the  various  modes  of  applying  that  agent  in  chemical  opera- 
tions. The  processes  dependent  upon  its  action  are,  princi- 
pally. Fusion,  Ignition,  Calcination,  Incineration,  Roast- 
ing, Deflagration,  Reduction,  Cupellation,  Sublimation, 
Distillation,  Digestion,  Decoction,  Boiling,  Solution, 
Evaporation,  Crystallization,  and  Desiccation. 

Furnaces. — Laboratory  furnaces  differ  in  construction  ac- 
cording to  the  uses  for  which  they  are  designed.  The  main 
parts  of  every  furnace  are  the  body  in  which  the  heat  is  pro- 
duced, the  grate  or  bars  upon  which  the  fuel  rests,  the  ash 
pan  for  receiving  the  residue,  and  smoke  pipe  for  conducting 
off  the  gaseous  products  of  combustion. 

The  stationary  furnace,  Fig.  6,  answers  very  well  for  ge- 
neral purposes,  but  is  less  convenient  in  a  small  laboratory 
than  a  portable  furnace.  When  the  former  is  not  possessed 
by  the  chemist,  the  sand  bath  may  be  constructed  as  directed 
at  p.  56,  or  in  default  of  gas  as  a  heating  medium,  the  top 
of  the  stove  (p.  39)  may  serve  as  a  substitute.  Such  an  ar- 
rangement is  cleanly  and  economical,  and  does  away  with  the 


150 


SOURCES  OF  HEAT — FURNACES. 


Fig.  87. 


necessity  of  cumbersome  brick  work.  It  has  also  the  advan- 
tage of  being  ready  at  all  times  for  use,  and  is  all-sufficient 
for  the  purposes  of  analysis  in  a  private  experimental  labora- 
tory. 

It  is  useless  to  multiply  furnaces  in  a  small  laboratory,  for 
they  occupy  room  which  may  be  wanting 
for  other  purposes,  and  therefore,  a  selec- 
tion should  be  made  of  one  which  in  its 
arrangement  is  applicable  to  all  the  ne- 
cessities of  the  chemist.  Of  this  kind, 
Luhme's  and  Kent's  are  the  best.  One  of 
either,  with  a  small  charcoal  furnace.  Fig. 
87,  such  as  may  be  bought  at  any  crockery 
shop,  for  table  use,  will  constitute  the  whole 
stock  required  of  this  sort  of  apparatus. 
Luhme's  furnace. — Figs.  88,  89  exhibit  this  furnace,  the 
cylindrical  form  of  which  is  to  be  preferred  on  account  of  its 
producing  a  higher  heat  with  less  fuel  than  any  other.  It 
is  of  strong  plate-iron,  and  lined  in  the  body  and  dome 
with  refractory  fire  clay.     Its  dimensions  are   twenty-four 


inches  in  height,  and  nine  inches  in  diameter.  The  body, 
a,  6,  c,  d,  is  capped  with  a  ring  of  the  same  circumference  as 
the  clay  cylinder  beneath.  The  doors  are  shown  at  g  and  h. 
The  circular  openings,  x,  x,  opposite  to  each  other,  are  for  the 
passage  of  tubes,  and  when  out  of  use  can  be  closed  by  the 
plugs  accompanying  the  furnace  for  that  purpose.  The  inte- 
rior of  the  furnace,  as  seen  from  above,  is  shown  by  Fig.  90. 
The  knobs  e,  e,  e,  projecting  inwardly,  serve  as  supports  for 
vessels  which  are  smaller  than  the  mouth  of  the  furnace, 


luhme's  universal  furnace. 


151 


whilst  the  iron  juts,  d  d  d,  directed  outwardly,  are  rests  for 
the  larger,  this  arrangement  being  necessary  in  both  instances, 
to  the  perfection  of  the  draught.     The  iron  jacket,  Fig.  91, 


Fig.  90. 


Fig.  91. 


adapted  to  the  opening,  a  c?.  Fig.  88,  forms  a  support  for  the 
double  sand  bath.  Fig.  92,  for  retorts,  and  other  glass  vessels. 
The  slope  on  the  side  of  the  sand  bath  is  for  the  exit  of  the 
neck  of  the  retort;  and  the  circular  openings,  k  k  k  k,  Fig. 
93,  are  fitted  with  covers,  by  which  to  augment  or  decrease 
the  draught,  as  may  be  required. 

A  supplementary  sand  bath.  Fig.  94,  is  made  with  a  broad 
extent  of  surface  for  digestions,  evaporations,  &c. 


Fig.  93. 


Fig.  94. 


The  dome,  Fig.  95,  confers  the  power  of  a  wind  furnace 
when  high  heat  is  required.  As  this  chimney  becomes  too  hot 
to  be  handled,  it  is  removed  when  heated  with  suitable  tongs, 
the  form  of  which  is  shown  in  Fig.  96. 

The  relative  position  of  the  several  parts  of  this  furnace, 
we  give  in  the  annexed  drawing.     Fig.  97. 

Kent's  universal  furnace,  which  is  an  improvement  upon  the 
above,  is  shown  by  Fig.  98  in  front  and  side  views  at  A  and  B. 
The  body  is  fourteen  inches  high,  by  seven  inches  in  diameter, 


« 


152 


KENT  S  UNIVERSAL  FURNACE. 


and  in  material  and  general  construction  is  similar  to  Luhme's 
furnace.  There  are  six  doors: — one  at  the  base  for  the  ad- 
mission of  air,  another  in  the  middle  for  the  entrance  of  the 
fuel  and  for  the  reception  of  the  muffle  used  in  cupellation. 
The  door  in  the  dome  is  for  the  purpose  of  feeding  the  fire  in 
crucible  operations;  and  that  in  the  side,  at  the  top,  for  the 
reception  of  the  neck  of  a  retort,  or  of  the  sand  bath  c,  Fig. 
98.  The  two  lateral  openings,  opposite  to  each  other,  are  for 
the  passage  of  tubes,  or  of  an  iron  bar  as  a  support  to  the 
rear  end  of  the  muffle. 


Fig.  95. 


Fig.  96. 


The  two  sand  baths  for  distillation  and  evaporation  are 
seen  at  c  and  D,  Fig.  98. 

The  plugs  E  are  for  closing  the  two  circular  openings  bj 
which  it  is  coupled  with  the  pipes  connecting  it  with  the  labo- 
ratory flue.  In  crucible  operations,  the  smoke-pipe  should 
lead  from  the  top  opening,  and  in  evaporations,  from  the  aper- 
ture in  the  back.  The  openings  in  the  flue  must  be  above  the 
level  of  the  furnace. 


EVAPORATINO  AND  REVERBERATORY  FURNACES.    153 

Fig.  98. 


The  remaining  opening  at  the  base  is  for  the  introduction  of 
the  mouth  of  a  bellows,  by  which  it  may  be  converted  into  a 
blast  furnace. 

As  our  advice  is  to  select  a  single  furnace,  combining  in  its 
construction  the  power  and  convenience  of  the  several  differ- 
ent kinds  required  in  the  laboratory,  we  proceed  to  make 
known  how  Luhme's  or  Kent's  apparatus  may  be  adapted  to 
the  various  purposes  of  the  chemist. 

1.  As  an  evaporating  and  calcining  furnace, — As  very 
high  heat  is  seldom  required  for  evaporations,  the  body  of  the 
furnace  alone  answers  every  purpose.  For  small  operations, 
or  when  but  a  small  fire  is  required,  its  capacity  may  be  di- 
minished by  inserting  an  inner  cylinder  of  baked  clay.  To 
increase  the  draught,  all  the  doors  should  be  closed,  and  to 
augment  still  further  the  heat,  as  is  necessary  in  the  calcina- 
tion of  certain  substances,  the  dome  and  chimney  may  be 
used.  In  this  latter  case,  by  means  of  the  door  in  the  mid- 
dle, the  progress  of  the  operation  may  be  examined  without 
removing  the  chimney  dome,  or  cooling  the  interior  of  the 
furnace. 

The  sand  and  other  baths,  which  have  their  places  upon  the 
top  of  this  furnace,  serve  for  digestions,  evaporations,  &c.,  in 
vessels  which  require  the  abatement  and  equalization  of  the 
heat  by  intermedia. 

2.  As  a  reverberator^  furnace. — This  kind  of  furnace  is 
adapted  to  operations  demanding  a  high  temperature,  as  in 
the  heating  of  crucibles,  tubes,  &c.,  and  also  in  sublimation 

11 


154  WIND  AND  BLAST  FURNACES. 

and  similar  processes  requiring  the  application  of  a  steady  heat 
to  all  portions  of  the  vessel,  rather  than  a  very  great  heat  to 
any  one  part  of  it. 

Luhme's  or  Kent's  furnace  is  rendered  reverberatory  by  the 
use  of  the  dome,  which  allows  the  vessel  to  be  entirely  sur- 
rounded by  flame,  and  reflects  back  the  heat  upon  and  around 
its  whole  surface,  and  thus  by  equalizing  the  temperature,  pre- 
vents the  condensation  of  vapors  in  the  upper  parts,  an  im- 
portant object  in  distilling  from  beaked  vessels. 

Coke  or  charcoal  is  the  fuel  generally  used,  the  latter  being 
preferable  for  a  furnace  of  small  dimensions ;  and  the  draught 
may  be  increased  by  lengthening  the  chimney. 

The  crucible,  or  vessel,  must  be  placed  in  the  centre,  sup- 
ported upon  half  of  a  fire-brick,  in  such  a  situation  that  the 
cold  air  ascending  through  the  grate  may  not  prevent  the 
heating  of  its  bottom.  The  fire  is  then  kindled  and  main- 
tained by  fresh  supplies  of  fuel,  which  are  added  carefully  so 
that  they  may  not,  whilst  cold,  come  in  contact  with  the  hot 
vessel  and  occasion  its  fracture. 

3.  As  a  wind  furnace. — Wind  furnaces  are  used  for  the 
vitrification  of  mixtures,  reduction  and  fusion  of  metals,  and  for 
other  operations  requiring  a  prolonged  elevation  of  tempera- 
ture. 

The  combustion  is  urged  by  the  draught  of  a  flue,  and  the 
degree  of  heat  within  the  furnace  depends  upon  the  size  and 
height  of  the  chimney  into  which  this  flue  passes.  The  in- 
tensity of  the  heat  is  increased  by  so  proportioning  the  dimen- 
sions of  the  furnace  and  the  chimney  that  their  diameters  are 
equal,  and  the  height  of  the  latter  twenty  to  thirty  times  the 
diameter  of  the  former. 

Luhme's  or  Kent's  furnace  may  be  converted  into  a  wind 
furnace  by  putting  on  the  dome,  closing  all  the  openings,  and 
giving  a  free  access  of  air  to  the  grating  through  a  pipe  at- 
tached to  the  circular  nozzle  in  the  hearth  space,  and  leading 
into  one  of  the  flues  of  the  laboratory  chimney.  The  smoke- 
pipe  may  lead  into  the  same  flue,  and  both  should  be  fitted 
with  dampers  for  the  regulation  of  the  draught. 

4.  As  a  blast  furnace. — Blast  furnaces  are  serviceable  for 
expeditiously  producing  a  great  intensity  of  heat,  and  are 
used  for  fusions  and  other  operations  which  require  more 
power  than  that  of  the  wind  furnace. 

The  combustion  is  urged  by  a  current  of  air  forced  through 


THE  ASSAY  OR  CUPEL  FURNACE.  155 

a  pair  of  double  bellows,  the  nozzle  of  which  leads  into  the 
circular  opening  near  the  base  of  either  of  the  aforenamed 
furnaces.  The  connection  should  be  tightly  adjusted  with 
LUTE,  so  as  to  prevent  any  escape  of  air.  The  arrangement 
otherwise  is  exactly  the  same  as  for  the  wind  furnace. 

In  blowing  the  blast,  let  the  stream  of  air  entering  the  fur- 
nace be  small  at  first,  and  be  gradually  increased  as  the  tem- 
perature becomes  higher.  The  maximum  heat  can  be  hasten- 
ed by  weighting  down  the  bellows,  and  thus  augmenting  the 
force  of  the  blast. 

Sefstrom's  {Berzelius,  vol.  8),  and  Aikin's  (Faraday^  p.  95), 
blast  furnaces  are  said  to  give  heat  sufficient  to  melt  felspar. 

The  blast  may  be  furnished  to  the  preceding  furnaces  from 
the  pneumatic  table.  Fig.  30,  through  a  flexible  leaden  pipe, 
connected  at  either  end  by  means  of  coupling  screws.  As 
the  lead  pipe  might  be  softened  by  a  too  great  proximity  to 
the  heated  furnace,  the  opening  in  the  ash  pit  of  the  latter 
to  which  the  former  is  to  be  attached,  should  be  fitted  with 
about  two  feet  of  iron  gas  pipe  so  as  to  prevent  direct  con- 
tact. 

5.  As  an  assay  or  cupel  furnace. — The  same  arrangement 
which  is  directed  for  a  reverberatory 
will  convert  Luhme's  or  Kent's  into  a  Fig.  99. 

cupel  furnace;  the  only  additional  re-         ^ — 

quisite  being  a  muffle,  Fig.  99,  for  the  /^ 
reception  of  the  cupels  in  assaying  /  _ 
operations.  ^^^  '^^ 

A  very  convenient  and  effective  fur- 
nace for  CUPELLATION,  is  shown  in  views  by  Figs.  100,  101. 

It  is  made  of  refractory  fire  clay,  and  hooped  with  strong 
iron  bands  fastened  together  by  screws  in  order  that  it  may 
better  withstand  the  high  temperature  to  which  it  is  subjected. 

A,  A^,  is  the  ash-pan,  of  diameter  sufficient  for  the  reception 
of  the  body  of  the  furnace  b  b'.  The  door,  c,  is  for  the  exit 
of  the  cinders,  and  the  ingress  of  the  air.  The  larger  open- 
ing, d',  in  the  body  of  the  furnace,  is  for  the  introduction  of 
the  muffle,  and  a  corresponding  one,  D,  opposite,  for  a  prism- 
shaped  support  of  baked  clay  for  maintaining  the  muffle  in  a 
horizontal  position.  The  mouth-piece,  supported  by  a  small 
platform,  affords  the  facility  of  admitting  or  preventing  the 
access  of  air  to  the  interior  of  the  muffle. 

There  are  other  openings  throughout  the  circumference  of 


156 


LIEBIG  S  FURNACE. 


the   body  immediately  above  the  grate,  for  increasing  the 
draught  when  necessary. 


Fig.  100. 


Fig.  101. 


In  the  part  of  the  dome  e  is  a  door  for  the  introduction 
of  the  fuel.  The  two  openings  e  e  are  for  the  introduction  of 
a  poker  to  arrange  the  fire. 

At  the  top  of  the  furnace  is  a  dome  G  G,  to  which  is  adapt- 
ed a  sheet  iron  pipe  for  increasing  the  draught. 

A  sliding  door  H  and  a  small  circular  gallery  i  ^,  as  a  sup- 
port for  heated  coals,  afford  additional  means  of  increasing 
the  draught. 

Furnaces  of  this  kind  may  be  had  at  the  pottery  of  Haig 
&  Co.,  or  of  A.  Miller,  of  this  city,  reference  being  given  to 
the  form  and  directions  in  this  book. 

Liehigs  furnace. — This  is  a  small  sheet  iron  furnace  with 
movable  partitions  and  screen,  in  which  the  combustion  of  or- 


MANAGEMENT  OF  FURNACES. 


157 


Fig.  102  shows  its 

Fig.  102. 


ganic  bodies  is  effected  by  a  charcoal  fire, 
interior.  Fig.  103  gives  a  side 
view  of  the  furnace  containing 
a  combustion  tube  under  pro- 
cess connected  with  organic 
analysis.  It  is  twenty-four 
inches  in  length,  three  inches 
in  height,  and  three  inches  in 
width  at  the  bottom,  diverging  to  four  inches  at  the  top. 

Fig.  103. 


Fig.  104.        Fig.  105. 


The  combustion  tube  a  passes  through  a  circular  opening  in 
the  closed  end  of  the  furnace  and  rests  upon  sheet  iron  sup- 
ports. Fig.  104.  The  grate  consists  of  a 
series  of  slits  in  the  bottom  of  the  fur- 
nace which  are  distant  from  each  other 
about  half  an  inch.  The  sheet  iron 
screens,  Fig.  105,  are  used  to  confine  the 
fire  to  certain  parts  of  the  tube. 

The  furnace  is  used  upon  the  table, 
and  should  rest  upon  a  stone  of  length  nearly  equal  to  its  own. 

Management  of  furnaces. — All  furnace  operations  should 
be  conducted  under  the  stationary  hood,  Fig.  9,  so  that  the 
carbonic  acid  and  other  noxious  exhalations  may  have  an 
escape  from  the  laboratory,  and  the  sparks  and  heated  air 
emitted,  be  prevented  from  endangering  the  comfort  and 
safety  of  the  apartment. 

If  the  furnace  is  without  feet,  it  should  rest  upon  a  stone 
block,  and  never  directly  upon  the  floor  or  the  top  of  the 
table,  for  its  heated  bottom  may  occasion  a  conflagration. 

Coal,  coke  and  charcoal  are  the  fuel  most  used.  Coal  is 
the  least  available,  for  it  contains  sulphur,  and  yields  a  large 
amount  of  ash  and  clinker,  which  choke  the  grating,  and  it 
should  never,  therefore,  be  used  in  the  blast  furnace. 

Coke  and  charcoal,  separately  or  combined,  are  used  for 
all  the  furnace  operations,  the  former  being  preferable  for 


158 


THE  FURNITURE  OF  FURNACES. 


Fig.  106. 


Fig.  107. 


assays  at  a  high  temperature.  Weight  for  weight,  their 
amount  of  heat  is  nearly  equal,  but  the  greater  density  of  the 
coke  enables  it  to  give  more  bulk  for  bulk  by  ten  per  cent. 
Charcoal  ignites  most  readily,  but  coke  is  more  durable. 
Moreover,  when  of  good  quality  and  free  from  sulphurous  and 
earthy  matter,  it  gives  but  little  ash  or  clinker.  By  mixing 
the  two  together  we  obtain  the  good  qualities  of  both;  but 
charcoal  alone  is  preferable  for  heating  glass  and  porcelain 
vessels.  Before  using  the  coke  or  charcoal,  care  must  be  taken 
that  it  has  been  freed  from  dust  and  dirt  by  sieving,  and  that 
the  pieces  are  about  the  size  of  a  walnut,  so  that  they  may 
pack  away  neither  too  loosely  nor  too  compactly. 

All  of  the  fuel  should  be  kept  in  a  dry  place,  for  the  vapor 
arising  from  wet  coal  and  condensing  upon  the  surface  of  fra- 
gile vessels  which  are  being  heated,  will  be  apt  to  cause  their 
fracture. 

The  crucibles  should  be  placed  in  the  centre  of  the  furnace, 
upon  a  support  which  may  be  a 
piece  of  fire-brick  or  a  cast-iron 
trivet,  as  shown  by  Fig.  106.  This 
support  answers  also  for  stone-ware 
retorts;  but  a  preferable  form  for 
this  purpose  is  the  crow's-foot.  Fig. 
107.  The  size  of  these  latter  imple- 
ments is  regulated  by  the  proportions  of  the  vessels  which 
they  support. 

For  supporting  basins  and  flasks  over  the  evaporating  fur- 
nace, an  iron  trellis  of  strong  wire.  Fig. 
108  is  necessary.  A  series  of  these  iron 
trellises,  of  different  sized  meshes,  will 
be  found  convenient  for  adapting  the 
heat  to  glass  vessels,  tubes,  &c. 

In  placing  the  vessels  in  the  fire  or 
in  the  sand  bath,  they  must  be  made 
to  stand  firmly,  and  as  near  to  the 
centre  as  possible,  so  that  they  may 
be  equally  heated  all  around.  To  pre- 
vent damage  to  them  by  a  too  sudden 
rise  of  temperature,  the  fire  must  be 
urged  gradually,  and  when  the  operations  are  finished,  they 
should  be  left  to  cool  with  the  furnace,  or,  if  taken  out,  be 
transferred  to  a  cool  sand  bath,  so  that  their  refrigeration 
may  not  be  so  sudden  as  to  cause  fracture. 


Fig.  108. 


THE  FURNITURE  OF  FURNACES. 


159 


When  the  vessel,  to  be  heated  over  the  naked  fire,  is  of  less 
diameter  than  the  mouth  of  the  furnace,  this  latter  may  be 
proportionally  lessened  by  means  of  a  suitably  adapted  flat 
iron  ring.   These  rings  Figs.  109, 110,  are  also  useful  when  it  is 


Fig.  109. 


Fig.  110. 


required  to  concentrate  the  heat  of  the  furnace  in  the  centre 
of  the  vessel,  and  therefore  it  is  advisable  to  have  a  series 
of  them,  the  centre  openings  of  which  should  decrease  gradu- 
ally so  as  to  render  them  convenient  for  all  ^ized  vessels. 

Before  commencing  operations  the  furnace  must  be  entirely 
freed  from  ashes  and 

clinker,  and  the  coal  Fig.  ill. 

placed  around  the 
vessel  in  layers. — 
When  a  fresh  supply 
of  fuel  is  requisite, 
it  may  be  added 
through  the  doorway 
made  for  the  purpose. 
The  auxiliary  appa- 
ratus of  a  furnace, 
other  than  that  al- 
ready mentioned,  are 
an  ordinary  iron  po- 
ker for  clearing  the 
grate;  a  pair  of  tongs  bent  at  right  angles.  Fig.  Ill,  for  plac- 
ing the  crucibles  in  the  fire,  and  another  pair  curved  at  their 
ends  for  grasping  the  crucibles  around  the  body  and  remov- 
ing them  from  the  furnace,  if  necessary,  whilst  still  hot. 
Another  pair  of  common  fire  tongs,  Fig.  113,  is  convenient 
for  adding  the  lumps  of  coal. 

Fig.  113. 


Fig.  112. 


160  LAMPS. 

Lamps. — Lamps  are  convenient  and  economical  substitutes 
for  furnaces  in  table  operations.  Being  less  cumbersome  and 
more  cleanly  than  the  latter,  they  are  readily  manageable  and 
always  ready  for  use ;  and  they  also  afford  the  means  of  more 
rapidly  multiplying  results. 

The  amount  of  heat  to  be  obtained  by  these  instruments 
depends  upon  their  size  and  arrangement.  A  properly  con- 
structed lamp  may  be  made  subservient  to  all  the  require- 
ments of  the  nicer  heating  operations  of  the  laboratory,  from 
gentle  digestion  or  evaporation  to  those  processes  which  re- 
quire a  very  high  degree  of  heat. 

The  heating  power  of  the  flame  is  most  active  immediately 
beneath  its  summit,  and  the  vessel  should  be  gradually  brought 
into  direct  contact  with  that  portion.  The  vessel  should  be 
heated  more  gradually  in  proportion  to  the  thickness.  When 
thick  glass  or  porcelain  or  other  fragile  bad  conducting  ma- 
terial is  suddenly  heated,  the  heated  part  expands  while  the 
rest  does  not,  and  this  unequal  tension  of  two  adjacent  parts 
causes  the  cracking  or  fracture  of  the  vessel.  There  is,  there- 
fore, a  great  advantage  in  employing  glass  or  porcelain  ves- 
sels of  thin  structure,  for  the  heat  being  rapidly  conducted 
through  them,  the  liability  of  fracture  is  diminished.  As 
strength  is,  however,  often  required  and  thicker  vessels  must 
be  used,  the  above  principles  of  expansion  and  conduction 
must  be  remembered  when  they  are  employed. 

In  order  to  apply  a  small  fire  to  a  large  surface,  the  heat 
may  be  diffused  by  setting  the  vessel  in  a  sand  or  water- 
bath,  or,  which  is  convenient  and  more  cleanly,  a  plate  of 
sheet  metal  or  wire  gauze  may  be  placed  between  the  vessel 
and  the  fire.  It  is  safer  not  to  allow  the  vessel  to  touch  the 
plate  or  gauze.  Iron  or  brass  gauze  may  be  used,  although 
fine  copper  gauze  is  preferable,  because  more  durable. 

The  combustible  or  fuel  most  commonly  used  in  chemical 
lamps  is  alcohol,  though  pyroxylic  spirit  and  lamp  oil  are 
occasionally  employed. 

Alcohol  flame  gives  no  smoke  or  unpleasant  odor,  the  pro- 
duct of  combustion  being  only  carbonic  acid  and  water ;  while 
lamp  oil,  especially  where  the  supply  of  oil  to  the  wick  is 
insufficient,  produces  a  black  carbonaceous  deposit  upon  the 
bottom  of  the  vessel  which  occasions  a  loss  of  heat  by  radia- 
tion. 

The  alcohol  flame  moreover  does  not  have  the  same  inju- 


161 

rious  effect  upon  bodies  in  contact  with  it  as  the  oil  flame  with 
its  sooty  deposit;  nor  does  it  hide  from  view  the  contents  of 
test-tubes,  retorts  and  other  vessels  by  blackening  the  glass. 

A  strong  heat  may  be  obtained  from  alcohol,  but  in  tedious 
processes,  which  require  a  long-continued  uniformity  of  tem- 
perature, the  best  lamp  oil,  or  better^  olive  oil  may  be  used  in 
an  Argand  burner. 

Pyroxylic  spirit  is  less  objectionable  than  lamp  oil,  and 
more  so  than  alcohol.  The  many  advantages  of  the  latter, 
therefore,  give  it  the  preference  over  all  other  combustibles  as 
fuel  for  chemical  lamps.  It  should  be  of  about  the  sp.  gr.  of 
0.85.  Lamps  burning,  should  always  be  extinguished  before 
having  the  supply  of  fuel  renewed,  so  as  to  prevent  liability 
of  explosion.  The  spirit  is  then  gradually  introduced  from  the 
tubed  bottle.  Fig.  38,  p.  72,  until  the  reservoir  is  nearly  full. 
This  mode  prevents  its  running  out  and  diminishes  the  risk 
of  overflow  from  too  large  a  stream.  When  the  lamp  is  not  in 
use,  the  wick  should  always  be  covered  with  the  extinguisher 
to  prevent  loss  by  evaporation. 

The  tongs  accompanying  these  lamps  are  a  pair  Fig.  1 14. 
of  surgeons'  forceps  of  such  a  form  as  shown  by  Fig. 
114.  As  they  are  liable  to  become  oxidized  by  con- 
stant exposure,  it  is  better  to  have  their  prongs 
plated  with  silver.  This  precaution  lessens  the 
liability  of  debasing  the  contents  of  crucibles  with 
iron  oxide  which  may  become  detached  when  they 
are  handled  with  rusty  tongues. 

We  proceed  to  speak  of  such  lamps  as  are  suit- 
able to  laboratory  purposes. 

Glass,  Spirit  Lamp. — This  is  a  small  glass  lamp  like  the 
one  shown  in  Fig.  115.     The  body 
is  the  reservoir  for  the  alcohol.     To  Fig.  115. 

the  neck  b  is  adjusted  a  copper  circu- 
lar shield  c,  with  a  tube  in  its  centre 

H      for  the  passage  of  the  wick,  which 

K      should  be  of  cotton,  and  similar  to 

H|    that  used  for  tallow  candles.     The 

Hl  shield  should  rest  upon,  rather  than 

^B  within  the  neck,  otherwise  its  expan- 

^B  sion  by  the  heat  may  cause  the  break- 

^H  age  of  the  glass.     A  minute  opening 

^B  drilled  in  the  shield  is  also  requisite  for  the  escape  of  vapor 

I 


162 


HEATING  OF  TUBES  BY  LAMPS. 


in  case  the  alcoliol  should  become  heated.  The  glass  cap  a, 
ground  interiorly,  so  as  to  fit  hermetically  to  the  neck  of  the 
lamp  when  not  in  use,  prevents  the  evaporation  of  the  alcohol 
and  the  consequent  impregnation  of  the  wick  with  water,  which 
renders  its  relighting  difficult.  The  lamp  must,  however,  be 
invariably  extinguished  before  putting  on  the  cap. 


Fig.  116. 


Fig.  1 17. 


These  lamps  are  useful  for  heating  small  apparatus,  such 
as  test  tubes.  Figs.  116,  117,  and  reduction  tubes,  Fig.  148, 
and  for  larger  vessels  which  require  only  a  gentle  heat,  as 


shown  in  Fig.  118. 


Fig.  118. 


BERZELIUS*  SPIRIT  LAMP.  163 

Berzelius  Lamp.     Fig.  26  at  page  54  represents  this  lamp 
with  the  improvements  recommended  by  Mitscherlich  and  Lie- 


big.  It  should  be  made  of  thick  sheet  copper  or  brass,  and  brazed 
instead  of  being  soldered  together.  Its  form  is  that  of  an  Ar- 
gand  lamp,  with  a  circular  body  or  reservoir  g^  which  receives 
its  fuel  through  the  stoppered  opening  r.  The  mechanism 
contained  in  the  frame  work  s,  and  communicating  with  the 
cylinder  t  allows  the  elevation  or  depression  of  the  wick  at 
will.  The  only  communication  between  this  portion  of  the 
lamp  and  the  reservoir  is  by  a  small  tube  through  which  the 
alcohol  is  supplied  to  the  wick.  The  chimney  u  may  be 
movable  and  adapted  to  a  flattened  socket  soldered  to  the  side 
of  the  inner  circumference  of  the  reservoir,  or  else  be  hinged 
in  the  same  position  so  that  it  may  be  thrown  back  when  the 
lamp  is  to  be  lighted  or  trimmed.  Surmounting  the  chimney 
is  a  crucible  jacket  h  with  a  handle  q  adapted  to  the  socket  or 
thumb  screw.  The  crucible  with  its  movable  cover  d,  Fig.  120,  is 


164  CRUCIBLE  JACKET. — LAMP  SUPPORT. 

placed  in  the  centre  of  the  sheet  iron  jacket  upon  supports 
so  as  to  receive  the  full  force  of  the 
Fig.  120.  flame.     It  is  designed  to  protect  the 

crucible  from  all  air  save  that  which 
passes  up  the  chimney.     The  whole 
arrangement  is  shown  by  Fig.  120,  C 
/      r\      \  being  the  chimney  of  the  spirit  lamp, 

Yrr""^l'>\\  and  the  arrows  showing  the  direction 

IB  I    ^    \^  \  (jf  i]^Q  flame  which  passes  unobstruct- 

ed upward.  All  atmospheric  air  save 
that  which  passes  up  the  chimney 
being  excluded,  the  heating  power  of 
the  lamp  is  greatly  increased. 

The  lamp,  as  is  seen  by  the  figures, 
is  mounted  upon  a  fork  v,  which  slides 
upon  the  upright  of  the  support  h. 
This  upright  is  a  smooth  wrought  iron  or  brass  rod,  screw  cut  at 
its  lower  end,  and  firmly  fastened  to  the  walnut  foot  b  by  means 
of  a  nut.  The  foot  serves  as  a  ballast  and  at  the  same  time 
as  a  bed  for  a  large  capsule,  which  is  a  convenient  receptacle 
for  any  matter  which  may  be  accidentally  spilled  from  the 
heating  vessel.  The  pan  p  is  intended  for  the  same  purpose 
when  the  support  is  occupied  on  either  side.  There  are  other 
appliances  which  add  to  the  convenience  of  this  lamp.  They 
consist  of  thumb  screws  and  sockets  d  effor  holding  the  iron 
wire  rings  ml  i  k.  These  rings,  varying  in  diameter,  serve 
as  supports  for  the  vessels  employed,  and  to  steady  those 
which  are  tall  like  the  flask  shown  in  the  figure,  a  clamp 
/  is  requisite.  The  thumb  screw  to  which  the  rings  are 
attached  slide  upon  the  upright  rod  and  allow  the  elevation 
or  depression  of  the  heating  vessel  at  will.  The  iron  plate 
sand  bath  n  is  very  useful  for  digestions  in  beaker  glasses 
which  will  not  safely  bear  direct  contact  with  the  flame. 

The  fittings  of  this  and  all  other  chemical  lamps  should 
combine  lightness  with  strength  so  as  to  avoid  the  dissipa- 
tion of  too  much  heat  by  excess  of  metal. 

Fig.  121  exhibits  a  lamp  support  not  very  dissimilar  to  the 
preceding,  but  with  a  cast  iron  triangular  foot  5,  of  weight  suf- 
ficient to  prevent  the  lamp  from  being  upset  by  the  super- 
position of  heavy  vessels.  The  iron  triangle  c?  is  a  very 
convenient  substitute  for  the  ring  when  a  crucible  is  to  be 
heated,  as  that  shape  aff'ords  a  better  support.     The  rod  a  of 


LUHME  S  LAMP. 


165 


Fig.  121. 


brass  or  iron  is  from  twenty  to  twenty-four  inches  in  length. 
The  fork  g  for  the  lamp,  and  the  rings,  are  all  adapted  to  the 
thumb  screws  which  hold  them  steadily 
until  they  are  to  be  replaced  by  others 
of  different  form  or  size  for  different  and 
larger  vessels. 

A  very  convenient  modification  of  Ber- 
zelius'  lamp  for  boiling  in  large  vessels  is 
shown  by  Fig.  122.  It  is  supported  by 
three  feet  of  solid  brass.  Adjusted  to  its 
wooden  handle  is  a  brass  crook  for  support- 
ing the  necks  of  beaked  vessels,  retorts,  and 
the  like.  This  crook  can  be  lowered  or 
elevated  at  will  by  means  of  the  thumb 
screw  by  which  it  is  fastened.  Two  rings 
accompany  it,  one  of  open  work  for  the 
support  of  capsules,  broad  and  round  bot- 
tomed vessels ;  and  the  other  cullendered 
with  fine  holes  for  the  distribution  of  the 
heat  to  flat  bottomed  glass  vessels. 

This  is  a  powerful  lamp,  and  is  more  convenient  for  large 
vessels  than  the  lamp  mounted  as  before  described.     Luhme, 

Fig.  122. 


who  first  recommended  this  form,  also  advises  that  there  be 
no  direct  communication  between  the  reservoir  and  the  circu- 


166 


ROSE  S  LAMP. — HORSFORD  S  LAMP. 


lar  space  containing  the  wick,  because  such  an  arrangement 
is  promotive  of  accidents.  When  the  lamp  has  burned  for  a 
length  of  time  and  nearly  all  the  alcohol  is  consumed,  the 
reservoir  becomes  filled  with  vaporized  spirit,  which  may  ex- 
plode when  it  is  re-lit  after  being  refilled.  All  this  is  pre- 
vented by  forming  the  connection  by  means  of  a  tube.  The 
Berzelius  lamps  of  recent  manufacture  are  made  with  this 
improvement. 

Either  of  these  lamps,  and  all  others  in  which  spirit  is  con- 
sumed, must  be  provided  with  a  metallic  extinguisher  to  pro- 
tect the  wick  and  prevent  evaporation  of  the  alcohol.  This 
extinguisher  is  seen  in  Fig.  26. 

Rose  8  Lamp. — This  lamp,  also  constructed  upon  the  prin- 
ciple of  the  Argand  burner,  gives  an  intense  heat.     It  pos- 


Fig.  123. 


sesses  the  advantage  recommended 


by  Luhme  of  having  the  reservoir 
at  a  distance  from  the  burner,  so 
that  the  spirit  remains  unheated 
during  the  longest  operations.  The 
wick  is  regulated  by  a  rack  and 
pinion  as  in  the  Berzelius  lamps, 
and  its  mode  of  management  is  pre- 
cisely the  same.  Mr.  Kent,  of  New 
York,  who  manufactures  them,  an- 
nexes the  improvement  of  Prof. 
Horsford,  by  which  a  heat  is  pro- 
duced sufficiently  intense  for  bend- 
ing glass  or  fusing  carbonate  of 
soda  in  a  few  minutes.  The  cop- 
per reservoir  is  used  by  being  placed 
upon  a  tripod  accompanying  it,  and 
fitting  to  the  Rose  lamp  as  shown 
by  Fig.  124.  Three  fluid  ounces  of  alcohol  are  poured  therein, 
and  the  screw  plug  tightly  closed.  The  jet  is  cleaned  by 
probing  it  with  a  needle,  and  the  heat  of  the  lamp  is  applied 
until  the  alcohol  boils.  The  vaporized  spirit  passes  through 
the  jet,  and  when  the  chimney  is  on,  takes  fire,  and  produces 
a  blast  flame  of  great  power.  The  contents  of  a  platinum 
crucible  placed  about  half  an  inch  above  the  chimney,  as 
shown  in  the  figure,  becomes  fused  in  a  few  minutes. 

The  Russian  Lamp. — This  apparatus.  Fig.  125,  of  Russian 
invention,  and  similar  in  principle  to  Horsford's  "  Cambridge 


THE  RUSSIAN  LAMP. 


167 


Fig.  124. 


blast  lamp,"  is  said  by  Noad  to 
afford  a  very  powerful  heat  in  a 
few  minutes.  It  consists  of  a 
strong  double  brass  cylinder  or  box, 
the  interior  arrangement  of  which 
is  shown  by  the  dotted  lines  in  the 
cut.  A  piece  of  tube  terminating 
in  a  jet  passes  from  the  exterior  to 
the  interior  chamber,  rising  nearly 
to  the  top  of  the  former.  The  fuel 
is  supplied  through  the  aperture  5, 
closed  with  a  cork,  and  not  with  a 
brass  cap.  The  lamp  is  known  to 
be  fully  charged  when  the  spirit 
begins  to  flow  from  the  jet.  The 
inner  chamber  is  then  to  be  filled 
with  the  same  spirit  to  within  half 
an  inch  of  the  apex  of  the  jet. 
The  ignited  spirit  in  the  inner 
chamber  heats  that  in  the  outer, 
and  causes  it  to  boil,  and  the  pres- 
sure of  the  vapor  forces  the  boiling 
spirit  through  the  jet  in  a  powerful 
stream,  which  of  course  becomes 
immediately  inflamed,  and  acts  as 

an  energetic  blast,  producing  heat  enough  to  ignite  a  plati- 
num crucible  placed  above  it  to  whiteness.     The  triangle 
which  supports  the  crucible 
must   be   of  platinum,    and  Fig.  125. 

the  ringsupon  which  the  tri- 
angle rests  of  very  stout  iron 
wire  in  order  to  resist  the 
fusing  effect  of  the  flame. 

There  are  certain  precau- 
tions necessary  in  the  use  of 
this  lamp,  to  guard  the  opera- 
tor against  accidents.  Before 
introducing  the  alcohol,  it  is 
proper  to  be  assured  that  the 
jet  is  free  from  impediment 
by  blowing  through  it.  The 
cork  stopper  h  must  be  put  in  rather  loosely,  so  that  it  may 


168  THE  GAS  LAMP. — TABLE  BLOW-PIPE. 

offer  no  resistance  should  a  stoppage  occur  during  the  opera- 
tion. For  still  greater  safety,  that  part  of  the  lamp  should 
be  turned  from  towards  the  experimenter. 

Pyroxylic  spirit*  is  the  fuel  recommended;  and  it  is  said 
that  a  lamp  of  this  construction,  3J  inches  in  height,  and  3J 
in  diameter,  will  burn  with  a  charge  of  four  ounces  of  spirit 
for  thirty  minutes,  which  is  long  enough  for  most  fluxions 
with  carbonated  alkali. 

The  G-as  Lamp. — This  arrangement.  Fig.  27,  which  has 
been  fully  described  at  p.  54,  supersedes  all  other  heating 
apparatus  for  table  operations.  Crucibles,  capsules,  and  re- 
torts are  alike  readily  heated  by  it,  and  even  distillations  on 
a  large  scale  may  be  successfully  performed.  To  effect  the 
latter  object,  the  upper  half  of  a  black  lead  or  clay  crucible 
may  be  placed  around  the  lamp,  provided  with  an  opening  on 
one  side  for  the  beak  of  a  retort  to  pass  out.  The  lower  half 
of  the  crucible,  with  its  bottom  broken  off,  is  then  inverted 
over  the  whole,  and  the  hole  at  the  top  loosely  covered  to 
allow  of  the  escape  of  the  products  of  combustion.  By  this 
arrangement,  the  heat  of  the  flame  reverberates  through  the 
dome,  and  increases  the  effect  to  such  a  degree  that  several 
pounds  of  mercury  may  be  distilled  at  once  from  the  red  oxide. 

The  Table  Blow  Pipe. — This  table,  shown  in  Fig.  30,  and 
described  at  p.  59,  may  be  used  either  with  a  Berzelius  or 
Rose  lamp,  or  the  Argand  gas  burner.  Fig.  31.     Gas,t  when 

•  Pyroxylic  spirit  is  a  very  inflammable  alcoholic  compound,  obtained  as  one 
of  the  products  of  the  destructive  distillation  of  wood.  As  found  in  commerce 
it  is  impure.    (See  Ure  and  Turner.) 

f  As  the  use  of  alcohol  for  lamps  and  of  fuel  for  furnaces,  with  the  necessary 
attendance  upon  the  latter,  involves  a  considerable  expense,  annually,  even  in 
an  experimental  laboratory,  it  is  not  inappropriate  to  allude  here  to  an  economi- 
cal means  of  replacing  them  with  gas. 

The  material  which  may  be  used  for  this  purpose  is  the  refuse  fat  of  the 
kitchen,  a  gallon  of  which  in  its  melted  state  will  yield  100  cubic  feet  of  oil 
gas,  sufficient  to  feed  a  bat  wing  burner  for  upwards  of  seventy  hours. 

Its  greater  density  and  amount  of  olefiant  gas  give  it  superiority  over  the 
coal  and  rosin  gas.  Moreover,  it  would  be  difficult  to  adapt  an  apparatus  to 
the  manufacture  of  small  quantities  from  the  latter  materials.  Fig.  126  exhibits 
Kent's  portable  apparatus  for  the  manufacture  of  gas  from  grease.  It  consists 
of  a  wrought  iron  retort,  thirteen  inches  high  and  six  inches  in  diameter,  with 
a  large  opening  at  the  top  for  the  passage  of  lumps  of  coke  with  which  it  is  to 
be  three-fourths  filled.  The  coke  is  used  to  increase  the  extent  of  the  heating 
surface  so  as  to  facilitate  and  hasten  the  generation  of  the  gas. 

The  retort  is  to  be  heated  to  low  redness,  but  no  higher,  otherwise  the  gas 
becomes  decarbonized.  The  oil  is  supplied  to  the  retort  in  a  thin  but  constant 
stream  from  the  funnel,  through  a  small  hole  in  the  key  of  the  stop-cock.     The 


MANUFACTURE  OF  ILLUMINATING  GAS  FROM  GREASE.   169 


furnished  by  public  companies,  is  by  far  the  most  economical 
source  of  heat,  and  withal  is  powerful,  readily  manageable, 
and  cleanly.  For  all  the  nicer  ignitions,  fluxions,  and  fusions 
it  does  away  with  the  necessity  of  a  furnace,  which  is  less 
convenient,  and  requires  tenfold  the  time  for  its  action.  In 
five  minutes,  by  the  use  of  this  implement,  we  can  often  satis- 
factorily complete  processes  which  with  a  furnace  would  re- 
quire an  hour.  This  saving  of  time  and  fatigue  is  an  import- 
ant consideration  when  the  operations  are  to  be  multiplied  or 
rapidly  repeated.  It  is  applicable  to  all  the  purposes  of  igni- 
tion, fusion,  and  fluxion  of  limited  quantities  of  matter,  and 
by  "  driving  the  current  of  air  obliquely  and  somewhat  down- 
ward through  the  Argand  burner,  the  process  of  cupellation 
may  be  accurately  performed  on  three  hundred  grains  of  lead.'* 

retort  is  connected  by  an  iron  tube  with  a  copper  reservoir  immersed  in  cold 
water,  for  the  purpose  of  cooling  the  gas  and  collecting  a  portion  of  undecom- 
posed  oil  which  passes  over.  An  additional  receiver  renders  this  apparatus 
applicable  to  the  purposes  of  illumination  or  heating.  All  the  pipes  and  appli- 
ances for  either  are  furnished  with  the  apparatus  by  the  manufacturer,  to  order. 
The  retort  requires  to  be  occasionally  cleansed,  but  at  no  other  time  has  it  to  be 
necessarily  opened. 

Fig.  126. 


Large  vulcanized  India-rubber  bags  make  excellent  gasometers  for  small 
quantities  of  gas,  but  for  100  cubic  feet,  it  will  be  better  to  have  a  sheet  iron 
bell  well  payed  over,  internally  and  exteriorly,  with  plumbago  paint.  The  cis- 
tern for  its  reception  can  be  sunk  in  the  yard,  and  for  the  above  quantity  its 
dimensions  must  be  6^  feet  diameter  and  4^  feet  depth. 

12 


170 


CRUCIBLE  HEATED  OVER  BLOW-PIPE  FLAME. 


When  gas  is  used  it  is  only  necessary  to  bring  the  Argand 
burner,  Fig.  31,  over  the  jet  3,  Fig.  30,  and  to  depress  it 


Fig.  127. 


\ ^^J 1 

so  much  that  its  orifice  may  extend  a  short  way  into  the  flame 
for  heating  a  vessel  of  small  surface,  and  still  further  for  ves- 
sels of  greater  superficies.  The  gas  being  turned  on  and  in- 
flamed, the  treadle  is  then  worked  with  the  foot,  slowly  at 
first,  until  the  current  of  air  thus  forced  up  through  the  tube 
changes  the  white  and  quiet  flame  into  one  of  a  pale  reddish 
tint  and  ragged  outline.  If  too  much  air  be  driven  through, 
the  flame  becomes  bluish,  and  the  heat  becomes  less  intense. 

When  a  lamp  is  used,  it  is  necessary  that  it  should  have  a 
circular  Argand  burner,  which  is  to  be  placed  over  the  jet  3, 
in  such  a  position  that  the  orifice  of  the  latter  projects  through 
the  centre  of  the  burner,  just  beyond  the  top  of  the  wick. 
The  length  of  the  flame  being  proportional  to  the  elevation  of 
the  wick,  the  latter  must  be  adjusted  accordingly  by  the  screw 
and  rack  before  being  ignited.  The  flame  being  of  the  proper 
height,  the  treadle  4,  Fig.  30,  is  to  be  worked  at  first  slowly, 
for  the  heat  must  be  gradually  applied,  and  then  more  rapidly 
by  increasing  the  motion  of  the  foot  until  the  blast  produces 
a  buzzing  sound,  when  the  impulse  is  continued  or  moderated 
as  the  case  may  require. 

The  crucible  to  be  heated  is  placed  upon  a  wire  triangle, 


HARE  S  COMPOUND  BLOW-PIPE. 


171 


resting  upon  a  ring  of  an  upright  support,  as  shown  in  the 
figure,  and  is  placed  over  the  flame,  so  that  it  may  be  sur- 
rounded by  the  upper  or  hotter  portion  (blow-pipe).  If  the 
flame  is  smoky,  and  deposits  carbon  upon  the  sides  of  the 
crucible,  the  blast  must  be  increased  or  the  flame  lowered. 

The  operation  being  finished,  the  covered  crucible  is  left  to 
cool  before  being  opened. 

Oompound  Blow-Pipe. — This  apparatus,  known  as  Hare's 
oxyhydrogen  blow-pipe,  is  used  for  the  fusions  of  such  refrac- 
tory but  fusible  substances  as  resist  the  highest  power  of  the 
furnace.  Its  action  is  based  upon  the  intense  heat  produced 
by  the  ignition  of  combined  oxygen  and  hydrogen  gases. 

Dr.  Hare's  form  of  apparatus,  with  which  he  fused  twenty- 
eight  ounces  of  platinum  in  one  mass,  is  given  and  fully  treated 
of  in  his  Oompend,  and  also  in  the  Encyclopedia  of  Chemistry; 
but  our  remarks  will  refer  to  a  more  economical  instrument 
constructed  upon  the  same  principle. 

Fig.  128  exhibits  the  instrument  as  made  and  sold  by  Kent. 

Fig.  128. 


It  consists  of  two  vulcanized  India  rubber  bags  or  reservoirs, 
of  twenty  gallons  or  greater  capacity.  These  bags  are  very 
flexible,  strong,  and  portable;  one  of  the  above  size,  when 
empty,  occupying  but  a  very  limited  space.  They  are  filled, 
the  one  with  oxygen,  and  the  other  with  hydrogen  gas, 
each  being  fitted  with  a  connecting  screw  and  stop-cock,  by 


172 


GENERATION  OF  OXYGEN  GAS. 


which  they  can  be  adjusted  directly  to  the  generating  appa- 
ratus, as  shown  by  Fig.  129,  or  with  a  gasometer,  when  they 


are  to  be  charged.  The  communication  between  the  bags  and 
the  jet-pipe  above  the  table  is  by  means  of  the  flexible  India 
rubber  or  lead  tubes,  coupled  by  gallows  screws.  Fig.  above. 
The  jets  are  so  divided  within  the  pipe  that  the  gases  enter 
at  opposite  ends,  and  consequently  are  not  mixed  until  they 
meet  at  the  arm  of  the  jet,  which  is  so  arranged  that  it  can 
be  raised  or  lowered  on  an  ordinary  retort  stand.  By  this 
arrangement,  which  is  a  convenient  modification  of  the  old 
double  jet,  a  jet  of  oxygen  passes  through  the  centre  of  a  cir- 
cular flame  of  hydrogen,  the  mixture  and  consequent  explo- 
sion of  gases  being  avoided. 

The  gradual  efilux  of  the  gas  from  the  reservoirs  is  efifected 
by  superposed  weights — a  much  more  convenient  mode  than 
that  of  hydrostatic  pressure,  which  is  requisite  when  metallic 
reservoirs  are  used. 

The  two  gases  are  very  readily  prepared.  The  whole  ap- 
paratus for  oxygen  is  shown  in  Fig.  129.  The  retort,  a  thin 
copper  flask,  is  connected  with  a  brass  cap  and  neck  by  a  gal- 
lows screw. 

Four  ounces  of  good  chlorate  of  potassa,  and  one  ounce  of 
peroxide  of  manganese  are  mixed  together  and  placed  in  the 
retort,  the  cap  screwed  down,  and  the  joints  luted  with  pipe 
clay.  The  heat  of  a  Berzelius  lamp,  applied  as  shown  in  the 
figure,  drives  over  ten  gallons  of  pure  oxygen  in  fifteen 
minutes. 

The  lamp  may  be  removed  as  soon  as  the  gas  begins  to  be 


GENERATION  OP  HYDROGEN  GAS. 


173 


generated  and  pass  over  freely,  as  suflBcient  heat  will  be  re- 
tained for  the  completion  of  the  operation.  The  caput  mor- 
tuum  of  chloride  of  potassium  and  oxide  of  manganese  re- 
maining in  the  retort  can  readily  be  removed  by  water. 

Hydrogen  can  still  more  readily  be  obtained  from  a  self- 
regulating  reservoir.     Fig.  130  exhibits  the  apparatus  as  made 

Fig.  130. 


by  Kent.  The  copper  cylinder  which  he  uses  is  replaced  in 
other  similar  instruments  by  glass.  It  consists  of  a  japanned 
copper  cylinder,  9  inches  high,  and  6  inches  diameter,  with  a 
cover  and  bell  attached. 

Within  the  bell  hangs  a  basket  of  copper  wire,  which  is  to 
be  filled  with  about  }  lb.  of  zinc,  in  lumps.  The  outer  cylin- 
der is  to  contain  6  lbs.  of  cold  diluted  sulphuric  acid,  made 
with  1  part  acid  to  4  of  water. 

In  the  upper  part  of  the  bell  is  a  division,  forming  a  recep- 
tacle for  a  strong  solution  of  potash,  2  f.^  of  which  are  put 
into  it  through  the  opening  in  the  top,  which  is  then  to  be 
tightly  stopped. 

The  apparatus  being  adjusted,  and  the  stop-cocks  opened, 
the  dilute  acid  rises  in  contact  with  the  zinc,  and  generates 
hydrogen  gas,  which,  being  forced  through  the  potassa  solu- 
tions, becomes  washed  previous  to  its  exit  from  the  stop-cock 
into  the  bag.  An  hour  suffices  to  generate  twenty  gallons  of 
gas ;  and,  when  it  is  desired  to  arrest  the  operation,  close  the 
stop-cock  so  as  to  produce  an  accumulation  of  gas  in  the  bell, 
and  thus  displace  the  acid.  The  action  may  be  renewed  at 
any  time  by  opening  the  cock. 

Accompanying  this  apparatus,  as  shown  by  separate  figures 
in  the  cut,  are  two  convenient  addenda  for  other  purposes ; 


174 


SELF-REGULATING  GAS  RESERVOIR. 


one  a  jet,  with  platina  sponge  and  fixtures,  for  producing  an 
instantaneous  light,  and  the  other  for  bending  glass  tubes,  &c. 
Thej  are  both  readily  attached  to  the  stop-cock  by  their  screws. 
In  the  first  case,  the  gas  is  projected  against  the  platina 
sponge,  and  becoming  immediately  ignited,  affords  a  ready 
means  of  lighting  a  taper.  The  sponge,  when  not  in  use, 
should  be  kept  covered  and  dry. 

The  oxyhydrogen  blow-pipe  is  put  into  operation  by  first 
charging  the  bags  with  gases,  placing  on  their  weights,  letting 
on  the  hydrogen,  igniting  it,  and  passing  a  jet  of  oxygen 
through  the  flame  directed  upon  the  substance  under  process. 
This  substance  should  rest  upon  charcoal  or  fire-brick,  and 
in  a  cavity  drilled  for  the  purpose  so  as  to  prevent  its  being 
blown  away  by  the  force  of  the  blast.  For  the  same  reason, 
when  the  substance  is  in  powder,  it  is  necessary  to  moisten  it 
with  water,  and  compress  it  in  the  cavity.  The  charcoal  rest 
is  very  conveniently  supported  upon  one  of  the  sliding  rings 
(Fig.  131),  which  allows  the  facility  of  bringing  it  near  to  the 
orifice  of  the  pipe  where  the  combustion  takes  place. 

When  this  apparatus  is  used  for  the  purposes  of  illumina- 
tion, as  in  the  production  of  the  Drummond  light^  which  is 
produced  by  the  action  of  its  flame  upon  a  cylinder  of  lime, 
the  nozzle  of  the  blow-pipe  must  be  pointed  upwards,  so  that 
the  flame  may  have  full  play  upon  the  incandescent  earth. 


Fig.  131. 


Fig.  132. 


mSM 


SUPPORTS. — TRIANGLES. 


175 


Supports. — In  lamp,  table  furnace,  and  blow-pipe  opera- 
tions, vessels  are  maintained  over  the  fire  by  supports,  dif- 
fering in  material  and  construction  with  the  uses  for  which 
thej  are  destined. 

A  very  simple  and  economical  support  is  shown  in  Figs.  131 
and  132,  the  only  difference  between  the  two  being  in  the  shape 
of  the  foot,  one  being  rectangular  and  the  other  round.  It 
consists  of  an  upright  iron  rod,  from  20  to  24  inches  long,  and 
about  J  of  an  inch  or  more  in  diameter,  screwed  into  a  cast 
iron  foot,  and  fastened  beneath  by  a  nut.  The  three  project- 
ing rings,  of  iron  wire,  2,  3,  and  4  inches  in  diameter,  are  held 
by  thumb  screws,  which  permit  their  elevation  or  depression  at 
will. 

For  the  larger  stands  the  thumb  screw  is  of  iron,  and  of 
the  form  exhibited  in  Fig.  127  and  Figs.  133, 135,  h.  It  is  made 

Fig.  133. 


with  two  holes,  at  right  angles  to  each  other,  and  screws,  one 
for  the  reception  of  the  iron  upright,  and  the  other  for  the 
handle  of  the  ring,  which  can  readily  be  detached  and  replaced 
by  another  of  different  size.  This  form  of  screw  and  socket 
prevents  the  necessity  and  expense  of  having  the  rings  at- 
tached to  the  screws.  One  of  these  screws  will  answer  for  a 
series  of  rings,  and  the  latter  being  of  iron  wire,  the  operator 
can  readily  form  them  himself  of  any  required  shape.  With 
this  arrangement,  and  a  series  of  dif- 
ferent sized  rings,  the  support  is  con- 
venient for  all  its  purposes  without 
the  expense  of  a  socket  for  each  ring. 
When  the  rings  are  too  large  for  the 
vessels  to  be  heated,  their  diameters 
may  be  diminished  by  means  of  stiff 
wire  triangles.  Fig.  134.  They  are 
particularly  useful  for  the  support  of 
small  crucibles,  as  is  shown  in  Fig. 


Fier.  134. 


1Y6 


THE  UNIVERSAL  SUPPORT. 


Fig.  135. 


27,  p.  54.  There  should  be 
a  number  of  them  of  different 
sizes. 

Fig.  135  exhibits  what  is 
called  the  '^universal  support.'' 
The  foot  is  of  cast  iron,  and 
the  toes  twelve  inches  apart. 
The  upright  rod  is  of  iron,  36 
inches  long,  and  |  in  diame- 
ter. It  is  substantially  made 
for  the  support  of  heavy  cap- 
sules, retorts,  &c.  The  thumb 
screw  and  socket  h  are  of  solid 
brass  or  iron.  A  brass  vice, 
6  inches  long,  and  IJ  inches 
wide,  lined  in  its  mouth  with 
buckskin,  is  shown  at  g.  It  is 
fitted  by  the  arm  /  to  the  hole 
c,  and  serves  for  the  support 
of  heavy  retorts  and  other  beaked  vessels,  as  shown  in  the 
figure.  Three  solid  brass  rings,  of  from  4  to  7  inches  diame- 
ter, accompany  this  stand,  and  are  held  in  the  socket  d  by  the 
thumb  screw  a.  As  the  arm  of  each  of  these  rings  is  adapted 
to  the  socket,  one  may  replace  the  other  when  it  is  desired  to 
change  the  size. 

Wooden  supports  adapted  for  tube  arrangements,  made  of 
box  wood  or  hickory  and  lined  with  cork  or  buckskin  at  the 
parts  intended  for  grasping,  are  also  convenient  and  necessary 
pieces  of  apparatus.  They  consist  of  foot  rod  and  nut  simi- 
lar to  the  iron  supports.  Their  other  parts  are  a  wooden 
vice  (Gay-Lussac's),  Fig.  138,  for  supporting  the  necks  of  re- 


Fig.!  36. 


r\ 


Fig.  138. 


Fig.  137. 


^L 


"WOODEN  SUPPORTS. — RETORT  HOLDERS. 


177 


torts  and  other  beaked  vessels;  Grahn's  cylinder  holder,  Fig. 
137,  for  experiments  with  gases;  and  a  wooden  ring.  Fig.  136, 
as  a  rest  for  inverted  flasks.  Fig.  139  exhibits  an  upright 
retort  clamp  with  a  movable  joint  and  wooden  screw  by  which 
it  can  be  raised  or  lowered  at  pleasure.  The  stand  or  lower 
portion  is  similar  in  construction  to  D  E,  Fig.  142. 

Fig.  140  represents  another  support  with  two  sliding  arms, 
the  upper  one  of  which  is  a  filtering  stand,  and  the  lower  a 
tube  or  retort  holder.  The  funnel  supports  of  the  upper  arm 
are  adjusted  thereto  by  means  of  wooden  thumb  screws,  and 
may  be  removed  at  pleasure.  These  are  less  convenient  than 
the  single  filter  stand,  Fig.  141,  though  they  have  the  advan- 


Fig.  139. 


Fig.  140. 


Fig.  141. 


^i>^=. 


I 


tage  of  allowing  several  simultaneous  filtrations  upon  one 
arm,  and  thus  a  single  stand  may  do  the  service  of  three  or 
four  according  to  the  length  of  the  arm.  The  uprights  of 
these  supports  should  be  screw  cut  at  the  lower  end  and 
fastened  to  their  pedestals  by  means  of  nuts,  which  retain 
them  in  place  more  firmly  than  any  other  mode. 

Another  form  of  stand  is  that  known  as  Berzelius'  table 
support.  It  is  of  hard  wood  and  consists  of  a  loaded  foot  D, 
Fig.  142,  supporting  a  flat  disc  A,  which  by  means  of  its  leg 
and  the  thumb  screw  E  can  be  raised  or  lowered  to  any  desired 
height.  This  is  a  very  convenient  rest  for  a  small  lamp  or  fur- 
nace or  for  recipients  in  distillations  when  it  is  required  to  raise 
either  above  the  level  of  the  operating  table.  When  in  this 
or  other  cases  the  surface  of  the  supported  vessel  is  round,  it 


178 


TUBE  AND  BULB  RESTS. 


Fig.  142. 

i^^m 

1 

i^^i 

Fig.  143. 


Fig.  144. 


is  safer  to  steady  it  upon  a  braided 
straw  ring,  Fig.  143,  interposed  between 
its  bottom  and  the  disc. 

For  supporting  tubes  and  other  ves- 
sels horizontally,  the  disc  may  be  re- 
placed by  the  brass  crook  as  shown  in 
figure  144 ;  and  for  globular  vessels  and 
flasks  by  the  wooden  tripod.  Fig.  145. 
Each  of  these  pieces  is  adapted  to  the 
stand  D,  and  one  may  replace  the  other 
when  necessary,  the  screw  allowing  them 
to  be  raised  and  steadily  maintained  at 
the  required  height.  The  height  of  this 
instrument  when  drawn  out  to  its  full 
length  is  twenty  inches. 

As  a  support  for  large  evaporating 

vessels  over  furnaces,  an  iron  tripod,  Fig. 

146,  is  very  convenient. 

The  test  tube  stand  or  rack,  which  is 

the  only  support  that  remains  to  be  men- 

tioned,  has  been  alluded  to  before,  p.  54, 


Fig.  145. 


Fig.  146. 


Fig.  25.  A  smaller  one  for  table  use  is  shown  in  Fig.  147. 
It  consists  of  two  narrow  uprights,  say  ten  inches  high,  of 
thin  poplar  wood,  which  are  braced  together  by  three  shelves. 
These  shelves  are  perforated  throughout  their  length  with 
auger  holes  for  the  reception  of  the  test  tubes.  The  smaller 
and  shorter  tubes  occupy  the  upper  range,  the  interval  be- 


TEST  BACK. — BATHS. 


179 


tween  which  and  the  middle  shelf  Fig.  147. 

should  be  less  by  an  inch  than  that 
between  it  and  the  lower. 

The  manifold  uses  of  the  pre- 
ceding instruments  will  be  fur- 
ther explained  when  treating  of 
manipulations  to  which  they  are 
applicable.  At  present  a  familiar 
idea  may  be  obtained  by  reference 
to  Figs.  116,  118,  119,  and  to  the 
cut  below  in  which  several  of  them,  as  applied  in  operations, 
are  included. 

Fig.  148. 


P" 


CHAPTER    XII. 


BATHS. 


The  preceding  chapter  relates  to  apparatus  for  the  direct 
application  of  fire;  our  present  remarks  will  refer  to  the 
means  by  which  the  heat  is  moderated  and  diflfused  before 
it  is  allowed  to  reach  the  substances  under  process.     These 


180  CONSTRUCTION  OF  BATHS. 

means  consist  of  baths,  which  are  called  vapor,  water,  saline, 
metallic,  oil  or  sand,  according  to  the  nature  of  the  interposed 
bodies  employed. 

The  object  of  an  intermedium  is  to  prevent  a  too  rapid  ap- 
plication of  heat,  and  to  give  greater  uniformity  of  tempera- 
ture. Inequality  and  too  sudden  application  of  heat  being 
thus  provided  against,  the  fracture  of  vessels  and  ejection  of 
their  contents,  and  many  inconveniences  attending  other  modes 
of  applying  heat  are  avoided. 

Baths  are  very  convenient  for  heating  substances  which 
require  a  constant  and  somewhat  permanent  elevation  of 
temperature,  and  which  might  undergo  decomposition  over 
the  naked  fire.  The  temperature  to  be  obtained,  is,  however, 
only  limited,  but  by  a  proper  management  of  the  fire  any 
degree  of  heat  up  to  the  maximum  amount  which  the  inter- 
medium is  capable  of  receiving  from  the  means  employed,  can 
be  obtained. 

Baths  consist  of  two  vessels  of  difierent  diameters,  and 
they  may  be  either  of  metal,  stoneware,  or  porcelain.  The 
outer  jacket  receives  the  intermediary  body,  and  the  inner 
one  the  substance  to  be  heated.  As  generally  constructed, 
baths  are  made  with  but  one  jacket,  the  aperture  or  mouth 
being  of  diameter  corresponding  with  that  of  the  heating 
vessel  which  is  to  be  placed  over  it.  This  arrangement  obviates 
the  necessity  of  an  inner  jacket  and  also  of  the  transfer  of 
the  substance  which  is  being  heated. 

Baths  are  useful  in  operating  upon  organic  and  other  bodies 
easily  alterable  by  heat.  They  are  also  convenient  for  deter- 
mining the  melting  point  of  those  substances  which  are  fusible 
at  or  below  the  degree  of  heat,  which  can  be  imparted  to  the 
liquid  or  vapor  of  the  bath:  that  temperature  being  made 
known  by  immersing  a  thermometer  at  the  commencement 
of  the  fusion  and  noting  the  degree. 

In  the  fluid  baths  the  thermometer  may  be  permanently 
fixed  by  means  of  a  perforated  cork,  closing  a  circular  aper- 
ture in  the  lid.  Fig.  84  with  the  scale  upon  the  stem  exhibits 
the  most  suitable  form  of  the  instrument  for  this  purpose. 
The  difference  in  temperature  between  the  bath  and  the  heat- 
ing substance,  which  is  sometimes  very  considerable,  especially 
when  porcelain  or  glass  is  used,  may  be  diminished  by  keep- 
ing the  bath  always  covered.  If  the  vessels  have  smooth 
surfaces,  the  heat  obtained  previous  to  ebullition  is  much 


STEAM-BATH. — WATER-BATH.  181 

higher  than  in  the  opposite  case.  While  the  bath  is  in  use, 
care  must  be  taken  that  the  amount  of  the  liquid  in  the  outer 
vessel  remains  as  nearly  as  possible  the  same  throughout  the 
process,  and  the  loss  from  evaporation  or  exit  of  vapor  should 
be  replaced  by  frequent  but  gradual  additions  of  the  same 
fluid. 

Steam-hath. — This  apparatus  forming  a  fixture  of  the  labo- 
ratory has  been  fully  described  at  p.  42,  Fig.  11.  It  is  a 
convenient  arrangement  for  heating  those  substances  which 
would  be  alike  injured  by  the  direct  application  of  fire  or 
contact  of  steam.     It  aiTords  a  temperature  of  fully  212°  F. 

For  very  small  operations,  the  apparatus  of  Dr.  Ure,  Fig.  149, 
is  an    excellent  contrivance.  pjg  j49 

"  It  consists  of  a  tin  box  about  «  -« 

18  inches  long  by  12  broad  J\      - —      /[  ■ 

and  6  deep.     The  bottom  is      p^^^r-^ — Mn 

hollowed  a  little  by  the  ham-       ..k::::^. £i— 

mer   towards    its    centre,    in       ~ \/ 

which  a  round  hole  is  cut  of  :^       r —  ^"-^ 

five  or  six  inches  in  diameter.  \\    /     (^=^^ 

Into  this  a  tin  tube  three  or  \M  \ 

four  inches  long  is  soldered.  ^-^ ) 

This  tube  is  made  to  fit  tightly 

into  the  mouth  of  a  common  tea-kettle,  which  has  a  movable 
handle.  The  top  of  the  box  has  a  number  of  circular  holes 
cut  in  it  of  difierent  diameters,  into  which  evaporating  cap- 
sules of  platinum,  glass,  or  porcelain  are  placed.  When  the 
kettle  filled  with  water  and  with  its  nozzle  corked  is  set  on  a 
stove,  the  vapor  playing  on  the  bottom  of  the  capsules  heats 
them  to  any  required  temperature ;  and  being  itself  continu- 
ally condensed,  it  runs  back  into  the  kettle  to  be  raised  again 
in  ceaseless  cohobation.  With  a  shade  above  to  screen  the 
vapor  chest  from  soot,  the  kettle  may  be  placed  over  a  com- 
mon fire.  The  orifices  not  in  use  are  closed  with  tin  lids.  In 
drying  precipitates,  the  tube  of  a  glass  funnel  may  be  corked 
and  placed  with  its  filter  directly  into  the  opening  of  a  proper 
size.  For  drying  red  cabbage,  violet  petals,  &c.,  a  tin  tray 
is  provided,  which  fits  close  to  the  top  of  the  box  within  the 
rim  which  goes  about  it.  The  round  orifices  are  left  open 
when  this  tray  is  applied." 

Water-bath. — The  water-bath  is  used  for  heating  those 
substances  which  require  a  temperature  lower  than  that  of 


182  CONSTRUCTION  OF  WATER-BATH. 

boiling  water.  It  is  very  available  where  bodies  easily  de- 
composable by  high  temperatures  are  to  be  heated,  and  is  also 
useful  for  the  gradual  exhaustion  of  vegetable  and  other  sub- 
stances which  only  give  up  their  soluble  matter  after  long 
contact  with  the  warm  solvent  liquid.  Though  seldom  em- 
ployed for  the  purpose  of  reducing  the  temperature  very  low, 
it  may,  by  proper  management,  be  made  to  yield  any  inter- 
mediate temperature  from  32°  to  212°  F. 

Every  water  and  liquid  bath,  whatever  its  form  and  the 
purpose  to  which  it  is  to  be  applied,  should  be  so  constructed 
that  the  vaporized  portions  can,  if  necessary,  be  confined 
within  the  vessel  and  prevented  from  escaping  by  other  outlets 
than  the  safety  valve.  As  proximity  of  the  escaping  vapor 
might  be  injurious  to  the  substance  under  process,  the  escape 
pipe  should  have  its  exit  six  or  eight  inches  distant  from  the 
sides  of  the  vessel. 

Any  two  vessels  of  different  diameters,  one  within  the  other, 
may  form  a  water-bath,  provided  the  intervening  space  at  the 
bottom  and  sides  is  sufficient  to  contain  the  requisite  amount 
of  water.  Straw  at  the  bottom  and  sides  is  an  excellent 
means  of  steadying  the  inner  vessel  and  preventing  direct 
contact  of  its  surface  with  the  more  highly  heated  bottom  of 
the  outer  vessel,  a  result  which  would  cause  the  temperature 
of  the  inner  vessel  to  be  raised  above  that  of  the  surrounding 
water. 


Fig.  150. 


A  regularly  constructed  water-bath  of  convenient  form  is 
shown  in  Fig.  150.  "A  is  the  vessel  containing  the  water, 
a  the  inner  flange  for  the  support  of  the  evaporating  dish  B, 


CONSTRUCTION  AND  USE  OP  WATER-BATH.  183 

or  different  circular  rings  when  smaller  dishes  are  employed. 
c2  is  a  tube  furnished  with  a  stop-cock  for  the  escape  of  the 
steam,  which,  in  some  cases,  requires  to  be  carried  still  farther 
off  by  an  additional  tube  attached  to  it.  The  whole  apparatus 
may  be  heated  either  by  a  gas-stove  or  on  a  charcoal  furnace. 
The  water-bath  is  filled  about  half-full  with  water.  It  will  be 
seen  that  water-baths  with  cover  act  more  on  the  principle  of 
steam-baths  as  soon  as  the  quantity  of  water  which  they  con- 
tain is  small.  Care  must  be  taken  always  to  replenish  the 
evaporating  water  by  adding  fresh,  otherwise  not  only  the 
experiment  may  be  ruined,  but  the  bath  itself  become  seriously 
injured." 

Large  tin  cups  make  excellent  water-baths  for  flasks  and 
tall  vessels.  The  bottom  of  the  flasks  may  rest  upon  small 
straw  rings  which  prevent  contact  with  the  heated  tin  and 
serve  also  to  steady  them.  The  holes  in  the  lid  for  the  pro- 
trusion of  the  necks  of  the  flasks  also  assist 
in  this  latter  respect.  ^^^-  ^^^• 

A  very  convenient  little  bath  for  very  small 
operations,  is  shown  in  Fig.  151.  It  consists 
of  a  copper  capsule  a,  with  a  ledge  around  its 
interior  circumference  as  a  rest  or  support  for 
the  vessel  to  be  heated.  In  order  that  it  may 
be  applicable  to  capsules  of  any  size,  its  top  is 
fitted  with  a  series  of  thick  flat  copper  rings,  which  afford  the 
power  of  decreasing  the  diameter  of  the  outer  capsule  to  suit 
that  of  the  vessel  to  be  heated. 

The  whole  diameter  of  the  outer  vessel  is  about  7  inches, 
and  when  all  the  rings  are  placed  upon  the  top  the  opening 
in  the  centre  is  about  1  inch,  but  by  withdrawing  one  at  a 
time  the  size  of  the  mouth  can  be  increased  gradually  from  1 
to  6J  inches  and  adapted  to  any  vessel  of  intermediate  size. 
It  would  be  well  to  have  a  small  tube  projecting  from  the  side 
so  as  to  answer  at  the  same  time  the  purpose  of  a  handle,  and 
of  an  exit  pipe  for  the  waste  vapor. 

This  apparatus,  as  is  seen  in  the  figure,  is  mounted  upon  a 
tripod  6,  a  convenient  support  when  the  small  spirit  lamp  is 
used  to  heat  the  water.  When  a  stronger  heat  is  required  it 
can  be  detached  and  mounted  upon  a  larger  support  and 
placed  over  the  gas  or  Berzelius  lamp.  Fig.  152  represents 
the  apparatus  without  the  tripod  and  with  handles. 

A  porcelain  or  tin  plate  placed  upon  the  top  of  this  bath 


184 


SALINE  BATHS. 


Fig.  152. 


renders  it  very  convenient  for  drying  small  filters,  precipi- 
tates, &c.  By  increasing  the  circumference  of 
the  bath  so  that  it  may  have  a  broad  top,  and 
by  piercing  the  latter  with  circular  holes  of 
various  diameters,  we  obtain  a  means  of  heat- 
ing several  capsules  of  different  sizes  at  the 
same  time.  Water-baths  are  useful  for  ex- 
hausting organic  and  other  matters  readily 
destructible  by  heat.  For  the  completion  of  evaporations 
which  have  been  carried  to  the  safest  extent  upon  a  sand-bath, 
they  are  also  very  available. 

The  still,  Fig.  13,  without  its^head  makes  an  excellent  water- 
bath  for  large  operations. 

Saline  baths. — The  substitution  of  saline  solutions  for  water 
affords  a  means  of  obtaining  temperatures  higher  than  the 
boiling  point  of  that  liquid.  This  kind  of  bath  is  very  useful 
for  digestions  and  many  other  operations.  The  saturation  of 
the  water  with  salts  raises  its  point  of  ebullition,  but  in 
practice  it  is  necessary  to  use  weaker  solutions,  otherwise  the 
evaporation  of  the  water  would  be  continually  causing  the 
deposition  of  the  salt  and  the  solidification  of  the  liquid  to 
the  great  inconvenience  of  the  experimenter. 

The  following  table  exhibits  the  boiling  points  of  the  satu- 
rated solution  of  the  salts  most  generally  employed  for  this 
purpose. 

BOILING  POINTS  OF  SATURATED  SOLUTIONS. 


Alum     -        -        -        . 

-     220° 

Carbonate  of  potassa 

-     2840 

Muriate  of  ammonia 

-     236 

Chloride  of  zinc 

-     320 

Oxalate  of  ammonia 

.     218 

Rochelle  salt   - 

.    246 

Tartrate  of  ammonia 

-    230 

Sulphate  of  nickel  - 

.        -    235 

Chloride  of  barium 

-     222 

Chlorate  of  potass    - 

-    218 

Nitrate  of  baryta 

-    214 

Nitrate  of  potass 

-     238 

Acetate  of  copper    - 

.     214 

Quadroxalate  of  potass 

-     220 

Sulphate  of  copper  - 

-    216 

Acetate  of  soda 

-    256 

Acetate  of  lead 

-     212 

Nitrate  of  soda 

-    246 

Chloride  of  calcium 

.     220 

Biborate  of  soda 

.    222 

Sulphate  of  magnesia 

-     222 

Carbonate  of  soda    - 

-     220 

Cream  of  tartar 

.     214 

Phosphate  of  soda   - 

.     222 

Chloride  of  sodium 

-     224 

Nitrate  of  strontia    - 

-     224 

Tartrate  of  potassa 

.    224 

Sulphite  of  zinc 

-     220 

Sulphate  of  goda      - 

.        -    213 

Boracic  acid    - 

-     218 

Chloride  of  zinc  is  included  in  the  above  table,  because  of 
is  great  deliquescence  and  availability  at  temperatures  below 
320°  F.   Beyond  that  degree  it  gives  off  fumes  of  chlorhydric 


METALLIC — OIL — SAND-BATHS.  185 

acid  and  becomes  inconvenient  as  a  medium  for  the  commu- 
nication of  heat.  A  layer  of  oil  retards  the  evaporation  of 
the  water  and  promotes  the  elevation  of  the  temperature  of 
the  solution. 

The  selection  of  the  ^alt  for  the  bath  must  be  with  regard 
to  economy  and  the  nature  of  the  material  of  the  vessels. 
Corrosive  solutions  should  only  be  used  in  those  vessels  upon 
which  they  are  without  action.  The  construction  of  the  bath 
is  similar  to  that  shown  in  Fig.  150. 

Metallic  baths. — These  baths  are  only  convenient  for  small 
operations,  because  of  the  difficulty  of  supporting  the  weight 
of  a  large  amount  of  metal  and  of  keeping  the  heating  vessels 
immersed  in  it.  They  furnish  temperatures  higher  than  either 
of  the  preceding,  and  for  greater  safety  must  be  heated  in 
cast  iron  vessels  of  form  suitable  to  the  experiment. 

Mercury  would  be  a  convenient  menstruum,  if  it  was  lighter 
and  emitted,  when  highly  heated,  less  noxious  fumes.  On 
these  accounts  it  is  but  rarely  used,  and  only  in  test  tubes  for 
heating  still  smaller  tubes.  The  fusible  alloy,  composed  of 
eight  parts  of  bismuth,  five  of  lead,  and  three  of  tin,  forms  an 
excellent  metallic  bath.  It  melts  below  212°  F.,  and  afibrds 
very  high  temperatures,  for  though  it  oxidizes  upon  the  sur- 
face as  its  temperature  is  increased,  it  will  bear  a  white  heat 
without  emitting  vapors.  Tin  melting  at  441°  F.  and  lead 
at  609°  F.,  are  both  available  for  a  temperature  above  their 
fusing  points. 

Oil  baths. — Oils  in  ebullition  throw  off  a  very  disagreeable 
vapor,  but  are  otherwise  convenient  for  furnishing  tempera- 
tures above  their  boiling  point.  Care  should  be  taken  not  to 
apply  heat  sufficient  for  their  decomposition.  Even  at  low 
temperatures  they  have  the  advantage  over  water,  of  losing 
less  by  evaporation  and  of  affording  facility  in  regulating  the 
temperature  by  means  of  an  immersed  thermometer.  The  oil 
should,  before  its  transfer  to  the  bath,  be  heated  in  an  iron 
capsule  for  several  hours,  to  expel  moisture.  The  bath  consists 
of  a  porcelain  lined  or  metallic  jacket,  of  construction  exactly 
similar  to  that  of  the  water-bath.  It  affords  a  temperature  of 
570°  F.,  and  the  facility  of  determining  its  temperature,  for 
which  purpose  a  thermometer  is  a  necessary  accompaniment. 

Sand-bath. — This  bath  is  of  more  general  application  for 
laboratory  purposes  than  either  of  the  others.  Its  different 
forms  and  their  appropriate  uses  have  already  been  fully  de- 


186  THE  PORTABLE  LABORATORY. 

scribed  at  pp.  38,  39,  Figs.  8,  28,  92,  94.  Sand  is  used, 
because  it  is  a  better  resistant  of  sudden  changes  of  tempera- 
ture, and  affords  a  uniform  heat  greater  or  less  as  may  be 
required  than  that  of  the  water  baths.  Magnesia  and  ashes 
are  sometimes  substituted,  but  they  are  too  apt  to  be  driven 
about  by  the  least  current  of  air;  the  former  is  only  used  as  a 
bed  for  platinum,  or  porcelain  crucibles,  which  are  to  be  en- 
closed in  Hessian  crucibles  and  ignited. 

A  sand-bath  may  be  readily  constructed  by  filling  an  iron 
pot  with  sand  and  placing  it  upon  the  charcoal  furnace.  Fig. 
87,  or  upon  the  top  of  the  stove  which  heats  the  apartment. 
It  is  then  ready  to  receive  glass  or  porcelain  vessels  in  which 
the  processes  of  evaporation,  digestion,  or  distillation  may  be 
carried  on. 


THE  PORTABLE  LABORATORY. 

Having  referred  to  each  separate  implement  employed  as  a 
means  of  applying  heat  in  the  various  chemical  operations,  we 
now  call  attention  to  a  convenient,  compact,  and  really  elegant 
apparatus,  of  German  invention  and  construction,  which  may 
very  appropriately  be  styled  a  portable  laboratory.  It  com- 
bines within  a  less  space  than  four  square  feet,  every  requisite 
for  convenient  manipulations  in  any  process  for  which  a  fur- 
nace is  required. 

We  are  indebted  for  the  drawing  Fig.  153,  to  iHolir's 
Clommentar  ^tir  JJrensiscljen  JJljarmacopcE.  The  furnace  and 
grate  are  of  iron,  and  can  be  set  wherever  it  is  convenient, 
adjoining  a  flue.  The  accompaniments  are  a  tin  lined  copper 
still  with  pewter  head  and  worm,  a  block  tin  digesting  cup ; 
two  other  digesting  cups,  one  of  glass  and  the  other  of  por- 
celain, protected  exteriorly  by  copper  jackets.  A  large  tinned 
copper  evaporating  basin,  another  similar  basin  with  a  por- 
celain interior,  and  a  half  score  of  other  convenient  and  useful 
vessels.  The  furnace  is  so  constructed  that  the  furniture  may 
be  heated  either  by  the  naked  fire  or  by  steam,  a  generator 
for  which  surrounds  the  body  of  the  still.  The  cooler  for  the 
worm,  is  a  large  copper  cylinder  of  some  twenty  gallons 
capacity,  tinned  and  arranged  interiorly  and  fitted  with  pipes, 
adapting  it  to  all  the  purposes  of  maceration,  decoction,  solu- 


THE  PORTABLE  LABORATORY. 
Fig.  153. 


187 


tion,  and  ebullition.     A  sand-bath  for  heating  glass  and  por- 
celain vessels  also  forms  part  of  the  apparatus. 

Weiss  and  Schively,  No.  43  north  Front  st.  Philadelphia, 
have  lately  imported  an  apparatus  somewhat  after  the  plan 
of  our  drawing,  the  first  one  we  believe  that  has  appeared  or 
been  offered  for  sale  in  this  country.  We  cannot  too  highly 
commend  these  implements  to  the  attention  of  the  druggist. 


188         THE  MODE  OF  PRODUCINa  LOW  TEMPERATURES. 

Where  the  means  will  justify  the  outlay,  every  pharmaceutical 
workshop  should  be  provided  with  one.  It  would  not  only 
facilitate  the  preparation  of  products,  but  would  also  afford 
the  means  of  pursuing  investigations,  and  thus  of  inducing  the 
operator  to  contribute  to  the  advancement  of  science. 


CHAPTER    XIII. 

THE  MODE  OF  PRODUCING  LOW  TEMPERATURES. 

A  LOW  degree  of  temperature  is  often  as  necessary  in  some 
chemical  processes  as  an  elevated  one  is  in  others.  The 
means  of  obtaining  it  are  by  freezing  mixtures,  and  these 
mixtures  are  formed  of  materials  prone  to  liquefaction.  The 
abstraction  of  the  heat  requisite  for  this  purpose,  from  the 
bodies  with  which  they  are  in  contact,  produces  in  them  a 
corresponding  decrease  of  temperature. 

In  many  chemical  investigations  they  are  particularly  use- 
ful, especially  for  determining  the  freezing  point  of  substances, 
and  as  cooling  media  for  the  recipients  in  the  various  pro- 
cesses of  Distillation.  The  components  of  freezing  mixtures 
should  be  finely  pulverized,  and  the  whole  formed  as  rapidly 
as  possible.  Bulbs  and  small  vessels  with  their  contents  may 
be  cooled,  but  not  economically,  by  keeping  their  surfaces 
moistened  with  ether  or  some  other  very  volatile  matter 
which,  by  rapid  vaporization,  can  carry  off  a  large  amount  of 
heat. 

The  following  convenient  tables  by  Walker  and  Karsten, 
exhibit  the  composition  of  numerous  freezing  mixtures  and 
the  degree  of  cold  which  they  produce. 


® 


FREEZING  MIXTURES. 


189 


Table  I.    Consisting  of  Frigorific  Mixtures,  composed  of  Ice,  with  Chemical 
Salts  and  Acids. 


Mixtures. 

C  Snow  or  pounded  ice 

(  Muriate  of  soda         -  -  1 

(  Snow  or  pounded  ice  -  5 

<  Muriate  of  soda  -  -  2 
(  Muriate  of  ammonia  -  1 
C  Snow  or  pounded  ice  24 

J  Muriate  of  soda         -  10 

j  Muriate  of  ammonia  -  5 

(^  Nitrate  of  potash      -  -  5 

rSnow  or  pounded  ice  12 

<  Muriate  of  soda  -  -  5 
(_  Nitrate  of  ammonia  -  5 
C  Snow  -  -  -  -3 
(  Diluted  sulphuric  acid*  -  2 
5  Snow  -  -  -  -  8 
(  Muriatic  acid  (concentrated)  5 
C  Snow  -  -  -  -7 
I  Concentrated  nitrous  acid  4 
C  Snow  -  -  -  -  4 
(  Muriate  of  lime  -  -  5 
5  Snow  -  -  -  -  2 
(  Crystallized  muriate  of  lime  3 

Snow       -        -         -  -3 

Potash     -         -         -  -  4 


Thermometer  sinks. 


Degree  of  cold 
produced. 


2  parts  i 


to— 5° 


to— 12« 


to— 18° 


to  —25° 
I  From  4-32°  to  —23° 

From  4-32°  to  —27° 

From  4-32°  to  —30° 

From  4-32°  to  —40° 

From  4-32°  to  —50° 

From  4-32°  to  —51° 


55° 


59 


62 


72 


82 


83 


N.B.  The  reason  for  the  omissions  in  the  last  column  of  this  table  is, 
the  thermometer  sinking  in  these  mixtures  to  the  degree  mentioned  in  the 
preceding  column,  and  never  lower,  whatever  may  be  the  temperature  of  the 
materials  at  mixing. 

Table  II.  Consisting  of  Frigorific  Mixtures,  having  the  power  of  generating 
or  creating  Cold,  without  the  aid  of  Ice,  sufficient  for  all  useful  and  philo- 
sophical purposes,  in  any  part  of  the  world  at  any  season. 


Mixtures. 

C  Muriate  of  ammonia  -  5  parts 

<  Nitrate  of  potash      -  -  5  " 

^  Water      ...  16  " 

f  Muriate  of  ammonia  -  5  " 

J  Nitrate  of  potash      •  -  5  " 

]  Sulphate  of  soda       -  -  8  " 

[Water      ...  16  « 

C  Nitrate  of  ammonia 
(  Water      • 

S  Nitrate  of  ammonia 
Carbonate  of  soda     - 
Water     - 


Thermometer  sinks. 


From  -f  50°  to  4-10° 


Degree  of  cold 
produced. 


40° 


^From  -f  50°  to  4-4° 

?  From  +50°  to  -f  4° 
>  From  +50°  to  —7° 
•  Strong  acid  2  parts ;  water  or  snow  1  part,  by  weight. 


46 


46 


57 


190 


FREEZING  MIXTURES. 


Mixtures. 

(  Sulphate  of  soda 
(  Diluted  nitrous  acid* 
r  Sulphate  of  soda 
J  Muriate  of  ammonia 
J  Nitrate  of  potash 
[^Diluted  nitrous  acid 
C  Sulphate  of  soda 

<  Nitrate  of  ammonia 
(  Diluted  nitrous  acid 
C  Phosphate  of  soda   - 
(  Diluted  nitrous  acid 
C  Phosphate  of  soda    - 

<  Nitrate  of  ammonia 
(  Diluted  nitrous  acid 
C  Sulphate  of  soda 

(  Muriatic  acid  - 

(  Sulphate  of  soda 

\  Diluted  sulphuric  acidj" 


__  ^  ,  Degree  of  cold 

Thermomeier  sinks.  produced. 


^^^^^  I  From  +50°  to  —3° 

"  1 

"  J^From  -f50o  to  —10° 

"  J 

«  >  From  4-50°  to  —14° 

((  V 

"  ^From+50°  to— 12° 

"  >  From  4-50°  to  —21° 

I  I  From  -f  50°  to  0° 

II  I  From  4-50°  to  +3° 


53° 
60 

64 

62 

71 

60 
47 


N.  B.  If  the  materials  are  mixed  at  a  warmer  temperature  than  that  expressed 
in  the  table,  the  effect  will  be  proportionately  greater;  thus,  if  the  most  powerful 
of  these  mixtures  be  made  when  the  air  is4-85°,  it  will  sink  the  thermometer 
to-f2°. 

Table  III.    Consisting  of  Frigorific  Mixtures  selected  from  the  foregoing  tables' 
and  combined  so  as  to  increase  or  extend  Cold  to  the  extremest  degrees. 


Mixtures. 

C  Phosphate  of  soda    - 
<  Nitrate  of  ammonia 
^  Diluted  nitrous  acid 
C  Phosphate  of  soda    - 
^  Nitrate  of  ammonia 
(  Diluted  mixed  acids 

Snow 

Diluted  nitrous  acid 
( Snow       -         -         - 
^  Diluted  sulphuric  acid 
(  Diluted  nitrous  acid 
\  Snow       -         -        - 
(  Diluted  sulphuric  acid 
5  Snow       -         -         - 
I  Muriate  of  lime 
( Snow       ... 
(  Miuiate  of  lime 

Snow       ... 

Muriate  of  lime 


5  parts 

3 

4 

3 

2 

4 

3 

2 

8 

3 

3 

1 

1 

3 

4 

3 

4 

2 

3 


Thermometer  sinks. 
From  0°  to  —34° 

^From— 34°to— 50° 

I  From  0°  to  —46° 

i  From  —10°  to  —56° 

I  From  —20°  to  —60° 
(  From  4-20°  to  —48° 
^From4-10°  to— 54° 
I  From  —15°  to  —68° 


Degree  of  cold 
produced. 

34° 


16 

46 

46 

40 
68 
64 
53 


*  Fuming  nitrous  acid  2  parts ;  water  1  part,  by  weight, 
t  Equal  weights  of  strong  acid  and  water. 


FREEZING  MIXTURES. 


191 


Mixtures. 

C  Snow       -        -        -         -  1  part 

(  Crystallized  muriate  of  lime  2  " 

CSnow       -        -        -        -  1  « 

I  Crystallized  muriate  of  lime  3  " 

i  Snow       -         -        -        -  8  " 

(  Diluted  sulphuric  acid       10  " 


Thermometer  sinks. 
From  0°  to  — GG^' 
From  — 40°  to  — .73<' 
I  From  —68°  to  —91° 


Degree  of  cold 
produced. 

66° 


33 


23 


Remarks.  The  above  artificial  processes  for  the  production  of  cold  are  more 
efiective  when  the  ingredients  are  first  cooled  by  immersion  in  other  freezing 
mixtures.  In  this  way  Mr.  Walker  succeeded  in  producing  a  cold  equal  to 
100°  below  the  zero  of  Fahrenheit,  or  132°  below  the  freezing  point  of  water. 

The  materials  in  the  first  column  are  to  be  cooled,  previously  to  mixing,  to 
the  temperature  required,  by  mixtures  taken  from  either  of  the  preceding  tables. 

The  following  table  by  Karsten,  shows  the  diminution  of  temperature  in 
degrees  Fah.,  where  1  pt.  of  salt  is  dissolved  in  4  pts.  water : — 


FREEZING  MIXTURES. 


Salts. 

Nitrate  of  lead 

"  baryta  ------ 

Common  salt 

Sulphate  of  copper         --.--. 

"  potassa        -        I         -        -        - 

"  zinc   ------ 

"  magnesia    -         -         -        -         - 

Muriate  of  baryta 

Sulphate  of  soda  ------- 

Nitrate  of  soda 17-0° 

«  potassa  -         - 19-1° 

Chloride  of  potassium 21*3° 

Nitrate  of  ammonia       -         - 25-4° 

Muriate  of  ammonia 27*3° 

The  following  table,  also  by  Karsten,  shows  the  degrees  of  cold  produced  by 
dissolving  1  pt.  of  a  salt  in  4  pts.  of  a  saturated  solution  of  another  salt : — 


Degrees  of  cold. 

3-4° 
3-8° 
3-8° 
4-0° 
5-2° 
6-6° 
S-P 
8-1° 
-     •  14-6° 


Salts. 

Sat.  solution  of 

Degrees  of  cold 

Sal  ammoniac 

Common  salt 

-       15-1° 

" 

Saltpetre     - 

-       22-7° 

Saltpetre 

Sal  ammoniac     - 

-       17-5° 

«             .         , 

Common  salt 

-       16-9° 

« 

Nitrate  of  soda  - 

-       12-7° 

(C                          .                . 

«         baryta 

-       17-5° 

/   "         .      - 

lead   - 

-       17-1° 

Glauber'8  salt 

Common  salt 

8-5° 

Common  salt 

Blue  vitriol 

7-4° 

Nitrate  of  soda     - 

Sal  ammoniac    - 

-       16-4° 

(( 

Saltpetre     - 

-       16-6° 

i( 

Common  salt 

-       14-0° 

(( 

Muriate  of  baryta 

4-9° 

« 

Nitrate  of  lead    - 

-       ]4-4° 

Nitrate  of  baryta 

Saltpetre     - 

1-35° 

Sulphate  of  zinc  - 

Sulphate  of  potassa 

31° 

192  FUSION. — CRUCIBLES. 

The  following  table,  by  Karsten,  of  1  pt.  salt  in  4  pts.  of  a  saturated  solution, 
shows  an  increase  of  temperature : — 


Salts. 

Sat.  solution  of 

Degrees  of  heat. 

Common  salt 

Sal  ammoniac 

8-2° 

«        -        . 

Glauber's  salt 

.         -         .         31° 

«        .        . 

Saltpetre    - 

1-35° 

"        -        . 

Nitrate  of  soda 

6-8° 

Muriate  of  baryta 

(( 

115° 

By  mingling  solid  lead  amalgam  with  solid  bismuth  amalgam,  whereby  they 
become  liquid,  Orioli  obtained  39-6°  of  cold.  Dobereiner  mixed  204  pts.  lead 
amalgam  (103  lead,  -f-  101  mercury)  with  172  pts.  bismuth  amalgam  (71  bis- 
muth -|-  101  mercury),  and  obtained  a  diminution  of  from  68°  to  302;  and  by 
adding  to  the  same  202  pts.  more  of  mercury,  the  temperature  fell  to  17-6°.  By 
dissolving  the  powders  of  59  pts.  tin,  1035  pts.  lead  and  182  pts.  bismuth,  in 
808  pts.  mercury,  the  thermometer  falls  from  635°  to  14°. 


CHAPTER   XIV. 

FUSION. 

The  liquefaction  of  bodies  by  heat,  a  preliminary  step  to 
many  processes,  is  termed  fusion.  Igneous  fusion  applies  to 
the  melting  of  anhydrous  substances,  and  aqueous  fusion  to 
the  liquefaction  of  a  salt  in  its  water  of  crystallization. 

The  modes  of  performing  the  process,  and  the  material  and 
form  of  the  apparatus  employed,  vary  with  the  nature  of  the 
substance  to  be  acted  upon.  The  chief  point  to  be  attended 
to  is  the  selection  of  such  containing  vessels  as  are  not  inju- 
riously aflfected  by  the  fused  substance — and  which  do  not 
themselves  react  upon  their  contents. 

The  implements  for  fusion  are  called  crucibles,  the  smaller 
of  which,  for  the  less  refractory  substances,  may  be  heated 
over  the  gas  or  spirit  lamp.  To  effect  the  liquefaction  of 
bodies  difficultly  fusible  or  of  large  quantities  of  matter,  a 
FURNACE  is  requisite. 

The  size  of  the  crucible  should  be  proportional  to  the  quan- 
tity of  matter  to  be  heated  in  it.  It  is  best  that  its  capacity 
should  be  no  greater  than  sufficient  for  the  contained  substance 
with  enough  margin  to  allow  for  swelling  or  foaming. 

Crucibles. — A  crucible,  to  be  available  for  any  and  every 
operation  should  possess  the  quality  of  compactness  in  order 


CLAY — HESSIAN — LONDON — FRENCH  CRUCIBLES. 


193 


Fig.  154. 


to  resist  the  corrosive  action  of  fused  substances,  the  permea- 
bility of  gases  and  liquids,  the  fusing  power  of  intense  heat, 
and  the  tendency  to  fracture  by  sudden  changes  of  tempe- 
rature. 

It  is  impossible  to  combine  all  these  requisites  in  any  one 
kind  of  crucible. 

The  materials  of  which  crucibles  are  formed  are  either  pure 
clay,  or  clay  mixed  with  charcoal,  quartz,  graphite  or  coke,  to 
render  it  more  refractory.  Black  lead,  porcelain,  silver  or 
platinum,  have  each  and  all  their  appropriate  application. 

Olay  Crucibles. — The  Hessian  and  French  crucibles  are 
those  of  this  description,  which  are  most  used.  The  Hessian, 
so  called  from  the  place  of  their  manufacture  in 
Germany,  are  either  in  the  form  of  a  tapering 
cylinder  or  triangular,  and  are  of  that  kind  of 
crucible  most  commonly  found  at  our  drug  shops. 
They  are  met  with  in  nests  of  a  half  dozen  or 
more,  gradually  increasing  in  size  from  the  small- 
est (of  an  ounce)  to  the  largest,  of  pint  or  quart 
capacity. 

They  are  grayish  yellow  or  whitish,  rough  to 
the  touch,  and  should  give  a  clear  ring  when  held  by  the  bot- 
tom and  sounded  on  the  sides.  Being  hard  and  impermeable, 
they  are  very  useful  for  rough  fusions ;  but  the  silica  which 
they  contain  renders  them  unfit  for  metallic  oxides,  with  which 
at  high  heat  it  combines. 

The  Hessian  crucibles  require  careful  usage,  as  they  are 
liable  to  be  fractured  by  even  slight  changes  of  temperature. 
Therefore,  notwithstanding  their  great  cheapness,  the  London 
or  French  crucibles  are  more  preferable  for  nice  operations. 

The  London  crucibles  are  very  refractory,  regularly  formed 
with  smooth  surfaces,  and  will  endure  a  very  high  heat. 

The  French  crucibles.  Fig.  155,  which  are  manufactured 
by  Beaufaye,  of  Paris,  are  said  to  be  far  superior 
to  either  of  the  preceding.  They  are  whitish, 
well-shaped  and  smooth  throughout,  and  being 
nearly  free  from  oxide  of  iron,  and  less  rich  in 
silica,  are  applicable  for  the  fusion  of  nearly  all 
substances  except  certain  salts,  which,  owing  to 
the  porosity  of  the  crucible  material,  are  readily 
absorbed. 

Being  capable  of  supporting  extreme  heat  as  well 
as  sudden  changes  of  temperature,  they  are  very 


Fig.  155. 


194        BLACK  LEAD  CRUCIBLES. — BLUE  POTS. 

useful  for  the  reduction  of  oxides  and  fusion  of  metals. 
Borax,  glass  and  similar  substances  remain  perfectly  colorless 
when  melted  in  these  crucibles. 

The  mixture  of  graphite  or  coke  with  the  clay,  which  is 
found  in  those  of  Austin's  make,  renders  them  capable  of 
better  supporting  the  softening  influence  of  the  wind  furnace 
and  withstanding  the  most  sudden  changes  of  temperature, 
but  the  proportion  of  the  latter  must  not  exceed  33  per  cent., 
otherwise  its  combustion  by  the  fire  will  leave  the  crucible 
porous  and  fragile. 

As  metallic  oxides  are  reducible  when  hot,  by  contact  with 
carbonaceous  matter,  these  crucibles,  when  used  for  heating 
those  substances,  should  be  lined  with  a  thick  coat  of  clay 
paste  and  dried. 

Charcoal  is  the  only  proper  fuel  for  earthen  crucibles,  as 
coke  is  apt  to  form  scoriae  which  attach  to  the  crucible  and 
impede  the  draught. 

Black  Lead  Crucibles.  Blue  Pots. — Black  lead  or  plum- 
bago when  mixed  with  one-fourth  of  its  weight  of  refractory 
clay  becomes  capable  of  supporting  intense  heat  and  sudden 
changes  of  temperature.  The  chief  use  of  crucibles  made  of 
this  substance  is  in  metallurgy,  for  the  purposes  of  which  their 
smooth  surface  admirably  adapts  them.  They  are  not  suffi- 
ciently compact  for  the  fusion  of  salts. 

Porcelain  Crucibles. — Crucibles  of  this  material  are  very 
neat  implements,  but  by  reason  of  their  incapability  of  resist- 
ing even  slight  changes  of  temperature,  are  only  used  for 
purposes  to  which  those  of  more  refractory  material  are  for 
other  reasons  not  adapted.  For  heating  over  the  lamp  they 
must  be  small  and  thin.  In  analytic  and  nice  operations  they 
replace  platinum  in  many  processes  in  which  the  contents  act 
upon  that  metal,  for  example,  in  igniting  plumbic  precipi- 
tates, melting  metallic  oxides  with  sulphobases,  preparing 
enamels,  and  heating  metallic  oxides  which  are  reduced  easily 
in  contact  with  platinum. 

The  crucibles.  Figs.  156, 157,  used  directly  over  the  lamp, 
should  never  exceed  an  ounce  in  capa- 

Fig.  156.      Fig.  157.      g-^^^  f^j.    ^^gj^  ^i^i^    ^^Q    jjjQgl-    careful 

management  it  will  be  difficult  to  cool 
one  of  larger  size  gradually  enough  to 
prevent  its  breaking.  Berzelius  recom- 
mends their  insertion  in  platinum  cru- 
cibles as  a  means  of  diminishing  their 


KJ 


PORCELAIN — METALLIC  CRUCIBLES. 


195 


fragility.  The  French  porcelain  being  very  thin  and  light, 
and  a  better  supporter  of  sudden  changes  of  heat,  is  preferable 
to  the  Berlin  for  small  crucibles. 

The  impermeability  and  cleanliness  of  these  crucibles,  ren- 
der them  very  convenient  for  the  fusion  of  certain  nice  sub- 
stances, such  as  nitrate  of  silver,  potassa,  &c.,  in  large 
quantities,  and  as  it  is  impracticable  to  have  a  very  large 
platinum  crucible  in  private  laboratories,  one  of  porcelain  is 
substituted.  These  large  crucibles,  made  with  covers,  may 
be  of  either  of  the  forms.  Figs.  158,  159,  160,  and  of  Berlin 
porcelain,  which  is  similar  to  wedgewood-ware,  and  heavier 
and  cheaper  than  the  French. 


Fig.  158. 


Fig.  159. 


Fig.  160. 


Fig.  161 


^ 


The  large  crucibles,  varying  in  size  from  two  to  six  inches 
in  height,  and  from  one  to  four  inches  in  diameter,  may  be 
entirely  biscuit  or  else  glazed  only  internally,  and  if  heated 
over  the  fire  require  to  be  enclosed  in  a  refractory  fire-clay 
case,  as  shown  in  Fig.  161.  This  case  is  equally  useful  for  pla- 
tinum or  silver  crucibles  (Fig.  120),  as  it  gives  them  a  proper 
elevation  above  the  grate  and  prevents  contact  with  the  coals. 

For  the  heating  of  more  readily  fusible  substances  they 
may  be  imbedded  in  a  sand-bath  and  heated  up  gradually. 
If  allowed  to  remain  in  the  bath  until  it  has  cooled  the  lia- 
bility of  fracture  from  sudden  refrigeration  will  be  diminished. 

Some  of  the  crucibles  have  duplicate  covers,  one  of  which 
is  perforated  and  used  to  facilitate  the  escape  of  the  gaseous 
matter  generated  during  certain  processes. 

Metallic  Crucibles. — Cast  and  plate  iron,  silver  and  pla- 
tinum are  all  used  as  materials  for  crucibles. 

Iron  Crucibles. — For  the  fusion  of  silicates  and  certain 
seleniurets,  sulphurets  and  other  substances,  iron  crucibles 
are  very  convenient.  An  exterior  coating  of  clay  is  requi- 
site to  protect  them  from  the  oxidizing  action  of  the  air,  to 


196  IRON — SILVER — PLATINUM  CRUCIBLES. 

which  they  are  subjected  at  high  temperatures.     The  same 
object  may  be  eflPected  by  inserting  them  in  clay  crucibles. 

When,  however,  the  heating  is  not 
Fig.  162.  Fig.  163.       of  long  duration  nor  intense  they 

may  be  used  naked. 
O  \^=^^^        Those  of  wrought  iron.  Fig.  162, 

are  struck  up  from  a  single  piece  of 
thick  sheet  metal. 

Cast  iron  crucibles.  Fig.  163,  are 
cheaper,  and  equally  as  good  as 
wrought  iron  for  medium  tempera- 
tures, but  they  must  be  turned 
smooth  interiorly. 
As  some  of  the  constituents  of  stove  coal  exert  a  chemical 
action  upon  metal,  the  only  proper  fuel  is  charcoal. 

Silver  Crucibles. — Silver  crucibles  are  but  rarely  used,  save 
for  the  fusion  of  potassa,  soda,  and  for  the  preparation  of 
caustic  baryta  from  the  nitrate.  For  most  operations  they 
are  well  replaced  by  platinum.  For  acid  substances  their 
use  is  improper.  The  spirit  or  gas  lamp  is  the  heating  appa- 
ratus, but  the  heat  must  not  be  too  high  nor  of  too  long  dura- 
tion, for  the  silver  is  apt  to  become  brittle  in  spots  as  it 
assumes  a  crystaline  form  under  the  influence  of  long  con- 
tinued red  heat. 

Platinum  Crucibles. — Platinum  crucibles  are  of  more  ge- 
neral application  than  those  of  any  other  material.  They 
are  very  tough  and  infusible  at  any  heat  that  can  be  obtained 
from  the  gas  or  spirit-lamp,  the  almost  exclusive  means  em- 
ployed for  that  purpose.  As  they  are  liable  to  become  rough 
at  high  furnace  temperatures,  they  should,  when  exposed  to 
Buch  influences,  be  inserted  in  an  earthen  crucible,  and  sur- 
rounded by  a  bed  of  magnesia. 

Their  strong  resistance  to  the  action  of  chemical  re-agents 
renders  them  indispensable  in  many  operations,  which  it  would 
be  difficult  otherwise  to  perform.  They  vary  in  size  from  a 
fluidrachm  to  three  or  more  fluidounces  capacity,  the  latter 
being  as  large  as  is  necessary  for  any  pur- 
Fig.  164.  p^gg  -j^  ^  private  laboratory.     Their  form 

is  shown  in  Fig.  164. 
pJi^         The  crucibles  intended  to  be  heated  over 
r     1     the  lamp  must  be  of  very  thin  metal,  so 
that  they  can  be  weighed,  as  is  often  neces- 


D 


THE  CONSTRUCTION  OF  CRUCIBLES.  197 

sary,  in  a  delicate  balance.  To  give  strength,  however,  the 
bottom  must  be  thicker  than  the  sides.  Two  of  the  smaller 
sized  will  be  found  more  useful  than  one  of  the  larger.  In 
analyses  a  half  ounce  crucible  is  indispensable  for  the  ignition 
of  filters. 

The  cover  is,  as  seen  in  the  figure,  slightly  convex  exteriorly, 
and  ledged  around  the  circumference :  this  form  is  convenient 
when  the  vessel  is  to  be  entirely  closed  when  heated;  but  in 
certain  operations  in  the  wet  way  it  is  reversed,  so  that  the 
convex  side  may  look  inwardly  and  return  any  particles  of 
its  contents  that  may  be  projected  upwards,  by  a  too  sudden 
or  intense  elevation  of  temperature.  The  pin  running  through 
its  centre  is  the  knob  by  which  it  is  handled  when  cold  with 
the  fingers,  when  hot  with  the  tongs.  Figs.  114,  127. 

For  evaporation  the  crucible  takes  the  form  of  a  capsule, 
as  is  seen  in  Fig.  165,  which  represents 
one  with  a  lip  and  handle.  ^^s-  165, 

Unless  the  crucibles  are  made  of  per- 
fectly pure  metal,  and  are  hammered  out 
instead  of  turned,  their  power  of  enduring 
strong  heats  and  resisting  the  action  of 
chemical  reagents  will  be  impaired.     The  blisters  and  flaws 
which  appear,  after  use,  are  owing  to  impurity  and  bad  work- 
manship, and  are  to  be  removed  by  the  force  of  a  small 
hammer. 

When  the  crucible  becomes  cracked  or  perforated  it  can  be 
repaired  by  welding  on  a  layer  of  platinum  sponge,  biit  it  is 
far  better  to  have  it  melted  up  and  remodeled  by  a  manufac- 
turer.    (J.  Bishop,  Philadelphia.) 

Boiling  or  hot  water  loosens  adherent  saline  matters,  and 
fused  borax  or  muriatic  acid  will  remove  all  stains  which  do 
not  disappear  by  rubbing  with  sand  or  pumice  stone.  The  use 
of  sharp  pointed  instruments  will  be  apt  to  injure  the  crucible. 

The  experimenter  himself  can  in  any  emergency  readily 
form  a  crucible  out  of  platinum  foil  by  shaping  it  with  the 
thumb  or  a  small  hammer,  in  a  hemispherical  cavity  made  in 
a  board  for  the  purpose. 

Berzelius  {Traite  de  Ohimie,  vol.  viii.)  gives  the  following 
instructions  as  to  the  manner  of  using  platinum  crucibles. 

"  Dry  fusion  should  never  be  effected  in  platinum  crucibles: 
1st.  Caustic  alkalies,  nitrates  of  lime,  baryta  or  strontia  and 
alkaline  nitrates  always  attack  the  platinum.     Alkaline  sul- 


198  DIRECTIONS  FOR  HEATING  CRUCIBLES. 

phurets  or  sulphates  with  charcoal  are  still  more  injurious. 
Metals  when  heated  to  their  melting  points  alloy  with  it,  and 
hence  lead,  tin,  antimony,  &c.,  should  never  be  even  mode- 
rately heated  in  it.  Even  their  oxides,  especially  those  of 
copper,  lead,  bismuth  and  nickel,  reduce  at  a  hifrli  heat  by 
contact  with  platinum,  particularly  if  charcoal  is  present,  the 
two  former  at  a  lower  temperature  than  the  latter.  Gold, 
silver,  copper  and  others  can  be  reddened,  but  not  melted  in 
platinum.  Phosphorus  or  phosphoric  acid  and  carbon  readily 
attack  it.  Sulphate  of  lead  may  be  burned  oiF  in  it  with  care, 
but  for  the  chloride,  porcelain  should  be  used. 

Silica  may  be  ignited  in  platinum,  but  it  combines  with 
silicium  at  a  heat  beyond  redness,  and  therefore  they  should 
always  be  encased  when  heated  in  the  fire,  otherwise  if  in 
contact,  it  will  abstract  it  from  the  coals. 

Nearly  all  liquids  may  be  heated  in  platinum,  except  they 
contain  chlorine,  bromine,  iodine  or  nitro-muriatic  acid. 

For  the  fixed  alkalies,  gold  is  preferable  to  either  silver  or 
platinum,  upon  which  they  have  a  more  or  less  corrosive 
action. 

Directions  for  Heating  Crucibles. — All  the  larger  and 
coarser  crucibles  are  heated  in  furnaces.  Their  proper 
position,  a  vertical  one,  is  in  the  centre  of  the  grate  upon  a 
slight  elevation.  Ignited  coals  are  placed  at  the  bottom  of 
the  grate  and  covered  with  alternate  layers  of  unlit  coke  and 
charcoal,  of  nut  size,  until  the  crucibie  is  surrounded  up  to 
the  level  of  its  top  with  fuel.  When  the  crucible  is  to  be 
strongly  heated,  it  should  be  covered  and  the  fuel  heaped 
over  its  top.  In  all  cases  the  fire  must  be  gradually  raised 
and  steadily  kept  up,  and  the  furnace  only  opened  when  fresh 
additions  of  coal  are  necessary,  as  it  is  important  that  there 
shall  be  no  variation  of  the  temperature  in  its  interior. 

After  the  completion  of  the  operation,  the  crucible  should 
be  allowed  to  cool  with  the  furnace,  or  if  taken  out  imme- 
diately, placed  upon  a  brick  or  bed  of  warm  sand,  otherwise 
a  too  sudden  change  of  temperature  will  cause  its  fracture. 
The  furnace  tongs,  Fig.  112,  are  conveniently  shaped  for  this 
purpose. 

As  it  is  occasionally  necessary  to  poke  the  fire  in  order 
that  the  fuel  may  settle  previous  to  fresh  additions,  it  will  be 
well  to  give  the  crucible  a  firm  position  upon  a  stand  for  the 
purpose — the  half  of  a  fire  brick  for  instance,  so  that  in  the 


FUSION  OF  SUBSTANCES  UNALTERABLE  BY  HEAT  OR  AIR.   199 

settling  of  the  coal,  there  may  be  no  risk  of  its  being  upset. 
When  by  intense  heat  its  bottom  has  become  welded  to 
the  brick,  the  latter  can  very  readily  be  detached  by  a  gentle 
tap  of  the  poker. 

Most  of  the  common  crucibles  serve  only  for  a  single 
operation. 

Covers  may  be  made  by  inverting  a  smaller  crucible  over 
the  top ;  or  better,  by  making  a  dough  of  Stourbridge  clay, 
and  luting  it  on.  The  crucible  in  the  latter  case  must  not 
be  heated  until  the  cover  has  dried.  These  lids  have  a  tend- 
ency to  retard  volatilization  and  are  necessary  to  prevent  the 
entrance  of  falling  particles  of  coal  and  ashes.  For  the  escape 
of  gaseous  matter  a  small  perforation  in  the  centre  of  the 
cover  is  necessary,  but  in  intensely  hot  fusions  all  other  open- 
ings must  be  closed  with  lute. 

The  smaller  metallic  crucibles  are  almost  exclusively  heated 
over  LAMPS.  They  are  supported  upon  wrought  iron  rings. 
Figs.  12T,  133,  the  diameter  of  which  may  be  reduced  when 
necessary,  by  the  use  of  the  wire  triangles,  fig.  134,  of  the 
required  size. 

If  the  crucibles  are  very  small  they  may  be  heated  by  the 
mouth  blow-pipe.  For  the  larger  an  argand  spirit  or  gas 
lamp.  Fig.  27,  is  needed.  To  hasten  the  process  or  to  in- 
crease the  temperature,  the  table  blow-pipe.  Figs.  30,  127, 
is  convenient,  as  it  gives  a  powerful  blast. 

The  use  of  the  jacket.  Fig.  120,  is  an  additional  means  of 
still  further  economizing  and  increasing  the  power  of  the 
flame.  It  also  diminishes  the  loss  of  heat  from  the  crucible 
by  radiation,  especially  when  the  latter  is  covered.  In 
charging  the  crucibles,  the  contents  should  be  concentrated 
into  as  small  a  space  as  possible,  and  any  adherent  particles 
should  be  brushed  from  the  sides  with  a  feather.  When  the 
crucibles  are  emptied  of  their  fused  contents,  the  melted 
matter  may  be  made  to  flow  upon  a  smooth  and  clean  slab  of 
marble,  iron  or  other  proper  material — great  care  being  taken 
that  it  does  not  come  in  contact  with  any  moisture  or  damp 
substance. 

Fusion  of  Substances  unalterable  by  Heat  or  Air. — This 
class  comprises  a  very  large  number  of  substances,  among 
which  are  the  noble  metals,  &c.  The  crucible  employed 
should  be  kept  covered  as  well  whilst  cooling  as  heating,  and 
the  refrigeration  must  be  gradual  or  the  molten  matter  may 


200  FUSION  OF  SUBSTANCES  ALTERABLE  BY  HEAT  AND  AIR. 

spirt.  There  are  other  metals  again,  for  instance,  zinc, 
lead,  tin,  antimony,  and  bismuth,  which  at  high  temperatures 
oxidize  readily  upon  exposure.  In  such  cases  it  is  well,  in 
addition  to  keeping  the  vessel  closed,  to  cover  the  fluid  mass 
with  a  layer  of  powdered  charcoal. 

When  a  metal  is  in  process  of  fusion  it  is  imprudent  to 
make  fresh  additions  without  having  first  heated  the  material 
to  be  added,  for  the  sudden  entrance  of  cold  or  damp  matter 
into  the  hot  fluid  mass  will  cause  the  ejection  of  particles, 
and  perhaps  serious  inconvenience. 

In  the  manufacture  of  alloys  the  metals  should  be  well  in- 
corporated by  occasional  stirring.  When  iron,  and  indeed 
manganese,  cobalt,  nickel  and  chrome,  are  being  exposed  to 
high  degrees  of  heat,  the  crucibles  must  be  free  from  carbona- 
ceous matter,  otherwise  a  combination  may  ensue  at  high 
temperatures. 

Fusion  of  Substances  alterable  by  Heat. — For  the  treat- 
ment of  substances  which  melt  below  212°  F.,  the  water-bath 
is  convenient.  The  fusion  of  substances  such  as  wax,  resin 
and  fat,  immiscible  with  that  liquid,  may  be  facilitated  by  the 
direct  application  of  boiling  water,  as  they  can  be  readily 
removed  from  the  surface  to  which  they  rise,  with  a  ladle  or 
syphon  whilst  hot,  or  in  a  mass  if  allowed  to  cool. 

Substances  requiring  a  temperature  at  or  below  550°  for 
their  fusion,  may  be  melted  in  an  oil-bath. 

Alloys  containing  volatile  metals  should  be  heated  as  quickly 
as  possible. 

Certain  substances  which  volatilize  at  low  temperatures 
require  to  be  fused  in  closed  vessels.  Iodine  and  arsenic  are 
examples. 

A  tube  of  glass,  porcelain  or  metal,  according  to  the  nature 
of  the  substance,  is  the  best  form  of  apparatus  for  this  pur- 
pose. It  should  be  rounded  at  one  end,  and  after  the  intro- 
duction of  the  substance,  closed  at  the  other  over  the  blow- 
pipe. 

The  tube  must  be  heated  throughout  its  length. 

Fusion  of  Bodies  alterable  by  Air. — This  class  of  substances 
is  melted  in  seclusion,  the  air  being  shut  out  by  means  of  an 
intermedium  of  liquid,  powder,  or  fusible  matter.  Thus  potas- 
sium is  liquefied  under  naphtha ;  phosphorus  under  water,  and 
certain  other  substances  in  powdered  charcoal. 


FUSION  OF  DIFFICULTLY  FUSIBLE  SUBSTANCES. — IGNITION.   201 

The  covers  of  the  crucibles  in  these  cases  must  be  tightly, 
luted  SO  that  all  openings  may  be  closed. 

Fusion  of  difficultly  fusible  Substances. — All  substances 
which  resist  the  fusing  power  of  furnaces,  are  to  be  subjected 
to  the  more  intense  action  of  the  hydro-oxygen  blow-pipe. 


CHAPTER    XV. 

IGNITION. 

Substances  frequently  require  to  be  ignited  to  redness 
either  as  the  sole  process  of  their  preparation,  or  as  a  preli- 
minary step  to  subsequent  operations. 

Ignition  of  Filters. — In  analyses,  the  filters  containing  the 
insoluble  or  precipitated  substances  which  are  to  be  estimated 
are  ignited  or  "burned  off"  to  expel  carbonaceous  and  vola- 
tile matters,  before  being  weighed.  The  implements  for  this 
purpose  are  porcelain  or  platinum  crucibles,  either  having 
their  appropriate  application. 

As  it  is  necessary  that  the  filter  should  be  wholly  or  par- 
tially dry,  it  must  be  carefully  remoyed  from  the  funnel, 
so  as  not  to  lose  a  particle  of  its  contents,  compressed  be- 
tween the  folds  of  bibulous  paper,  and,  further,  dried  in  a 
capsule  over  a  sand  or  water  bath,  or  in  a  drying  stove  (De- 
siccation), at  a  temperature  of  about  200°  F.  or  less.  The 
dried  filter  is  then  to  be  transferred  to  the  crucible  which  has 
been  previously  weighed.  The  transfer  must  be  made  with- 
out the  loss  of  the  least  particle,  and  for  this  purpose  the 
crucible  may  be  placed  upon  a  sheet  of  glazed  white  paper, 
so  that  any  particles  that  accidentally  fall  may  be  pre- 
served. The  filter  should  be  placed  in  the  crucible  with  its 
apex  upwards,  after  having  been  freed  as  much  as  possible 
from  the  adherent  precipitate  by  gently  rubbing  the  sides 
together  between  the  thumb  and  forefinger.  The  force  used 
for  this  purpose  must  not  be  sufiicient  to  abrade  the  paper, 
otherwise  the  matter  will  reach  the  fingers,  and  a  loss  thus 
be  occasioned  by  adherence.  The  crucible  is  then  heated 
cautiously  and  gradually  over  the  spirit  or  gas  lamp.  Fig. 
14 


202  IGNITION  OF  BODIES  IN  VAPORS. 

127,  the  flame  of  which  may  be  urged  by  the  blast.  For  the 
first  few  moments  the  vessel  should  remain  covered,  for  fear 
of  loss  by  decrepitation,  but  as  soon  as  it  becomes  red-hot 
the  lid  may  be  wholly  or  partially  removed,  and  the  crucible 
slightly  inclined,  as  at  Fig.  27.  This  position  allows  the  free 
admission  of  air  and  the  complete  and  rapid  incineration  of  the 
filter.  This  done,  the  cover  is  replaced,  the  crucible  allowed 
to  cool,  and  then  weighed.  The  weight  of  the  crucible  and 
that  of  the  ashes  of  the  filter,  which  latter  has  been  previously 
determined  by  the  incineration  of  filters  of  difi'erent  sizes,  de- 
ducted from  the  total  weight,  gives  the  weight  of  the  ignited 
precipitate. 

When  substances  are  to  be  ignited  for  the  determination  of 
their  hygroscopic,  volatile,  or  organic  matter,  the  heat  of  the 
lamp  should  be  gradually  applied  without  the  blast,  and, 
for  the  former  purpose,  only  to  the  production  of  a  dull  red 
heat.  In  these  instances,  the  crucible  should  be  weighed  first, 
so  that  the  loss  sustained  by  a  given  weight  of  its  contents 
during  ignition,  may  be  ascertained  in  one  weighing  merely 
by  subtracting  the  weight  of  the  crucible  and  contents  after 
ignition  from  the  combined  weight  of  the  two  before  the  same 
process.     The  loss  gives  the  amount  of  volatile  matter. 

In  analyses  of  coals,  the  moisture  can  be  determined  by 
heating  the  crucible  in  a  hot  sand-bath,  or  very  gently  over 
a  low  flame.  After  the  loss  thus  occasioned  is  determined  by 
weighing,  the  amount  of  carbon  may  be  ascertained  by  sub- 
jecting the  crucible  and  contents  to  a  much  higher  heat. 

When  substances  are  to  be  exposed  to  heat,  the  crucible 
and  contents  must  likewise  be  weighed  separately  before  ig- 
nition. The  loss  of  weight  gives  the  amount  of  volatile 
matter  driven  off.  The  ignited  matter  can  then  be  removed 
from  the  crucible  by  hot  water  alone  or  acidulated. 

Scorise  may  be  removed  from  platinum  crucibles  by  covering 
them  with  a  paste  of  borax  and  carbonate  of  soda,  heating 
them  to  redness,  and  when  cold,  dissolving  out  the  saline 
matter  with  boiling  water.  A  repetition  of  the  process  is 
necessary  to  brighten  the  crucible  perfectly  if  it  had  been 
very  dirty. 

Ignition  of  Bodies  in  Vapors. — If  it  be  desired  to  heat 
a  fixed  substance  in  the  vapor  of  any  body,  which  is  solid  or 
liquid  at  ordinary  temperatures,  the  latter  may  be  put  into  a 
tube  closed  at  one  end,  or  into  a  small  flask  with  a  long  neck, 


IGNITION  WITH  FLUXES.  203 

and  then  be  heated  until  it  is  wholly  vaporized.  The  substance 
is  to  be  introduced  into  the  tube,  and  heated  in  the  vapor  at 
any  desired  temperature.  Thus,  to  show  the  affinity  of  sul- 
phur for  copper,  the  former  is  heated  until  its  vapor  fills  the 
whole  flask,  when  slips  of  copper  foil  let  down  into  it  imme- 
diately ignite  on  combining  with  the  sulphur.  When  a  tube 
is  used  it  may  be  held  in  any  inclined  position,  but  a  flask 
should  be  nearly  vertical. 

Ignition  with  Fluxes.—F\\i.xQ^  are  certain  substances  usu- 
ally saline,  mixed  with  other  bodies  in  order  to  promote  their 
fusion  or  decomposition  by  heat,  and,  to  render  them  more 
soluble  in  water  and  acids.  All  ignitions  with  fluxes  in  expe- 
rimental operations  are  performed  in  crucibles  over  the  spirit- 
lamp  or  furnace  fire,  and  for  the  fluxions  of  those  substances 
in  which  there  is  no  reducible  metallic  oxide,  platinum  is  by 
far  the  best  material. 

The  process  is  particularly  useful  in  the  analysis  of  the 
sulphurets  of  alkaline  earths,  of  many  silicates  and  other  ob- 
stinate compounds  and  also  in  metallic  operations. 

The  principal  objects  of  fluxing  are: — 

1.  "  To  cause  the  fusion  of  a  body,  either  difficultly  fusible, 
or  infusible  by  itself. 

2.  To  fuse  foreign  substances  mixed  with  a  metal,  in  order 
to  separate  the  latter  by  its  diff'erence  of  specific  gravity. 

3.  To  destroy  a  compound  into  which  an  oxide  enters, 
and  which  prevents  the  oxide  being  reduced  by  charcoal. 
The  silicate  of  zinc,  for  instance,  yields  no  metallic  zinc  with 
charcoal,  unless  it  be  mixed  with  a  flux  capable  of  combining 
with  the  silica. 

4.  To  prevent  the  formation  of  certain  alloys,  and  con- 
sequently the  combination  of  some  metals  with  others,  as  in 
the  case  of  a  mixture  of  the  oxides  of  manganese  and  iron 
with  a  suitable  flux,  the  iron  is  obtained  in  a  state  of  purity, 
w^hereas  if  no  flux  had  been  added,  an  alloy  would  have  been 
obtained.  Gold  and  silver  can  be  separated  from  many  other 
metals  by  means  of  a  flux. 

5.  To  scorify  some  of  the  metals  contained  in  the  sub- 
stance to  be  assayed,  and  obtain  the  others  alloyed  with  a 
metal  contained  in  the  flux,  as  gold  or  silver  with  lead. 

6.  And  lastly,  a  flux  may  be  employed  to  obtain  a  single 
button  of  metal,  which  otherwise  would  be  obtained  in  glob- 
ules." 


204  NON-METALLIC  FLUXES. 

Fluxes  should  always  be  pulverized,  and  whether  mixed 
directly  with  the  substance  before  ignition,  or  added  gradu- 
ally to  the  crucible  during  the  process,  ought  rather  to  be  in 
excess  than  in  deficiency.  In  the  fluxion  of  silicates  the 
material  and  flux  are  incorporated  together  before  being 
transferred  to  the  crucible. 

When  the  mixture  is  of  a  frothing  nature,  it  is  best  to  add 
it  to  the  crucible  piecemeal  and  to  heat  it  gradually,  so  as  to 
save  the  loss  caused  by  ejection  of  particles.  After  the 
whole  has  been  placed  in  the  crucible,  the  heat  may  be  raised 
and  maintained  until  perfect  fusion  and  the  completion  of  the 
process. 

Fluxes  are  divided  into  non-metallic  and  metallic  fluxes. 

Non-Metallic  Fluxes.  —  (Berthier,  JEssais  par  la  voie 
Seche.) — Silica  is  employed  frequently  to  cause  the  fusion  of 
some  gangues  in  assays  made  at  an  elevated  temperature. 
Silica  combines  with  all  the  bases,  and  forms  with  them  bodies 
termed  silicates,  which  are  more  or  less  fusible. 

Lime,  Magnesia,  and  Alumina. — It  is  known  that  no 
simple  silicate  is  readily  fusible,  so  that  lime,  magnesia,  or 
alumina  are  employed,  according  to  circumstances,  to  reduce 
a  simple  silicate  to  such  a  condition  that  it  will  readily  fuse 
in  an  assay  furnace.  Sometimes,  to  attain  this  end  it  is  re- 
quisite to  use  all  the  above-mentioned  earths,  for  experience 
has  proved  that  as  a  general  thing  a  mixed  or  double  silicate 
fuses  more  readily,  and  flows  freer  than  a  simple  silicate. 

Baryta. — Hydrate  of  baryta  fuses  at  a  low  red  heat,  and 
without  loss  of  its  water  of  crystallization,  and  for  the  first 
reason  is  preferable  to  either  the  carbonate  or  nitrate.  It  is 
used  in  silver  or  platinum  crucibles,  and  when  silicates  are 
to  be  tested  for  alkalies.  The  silicates  of  baryta,  however, 
fuse  with  difficulty,  and  are  sluggish. 

Grlass  is  a  very  useful  flux  in  certain  iron  assays.  The 
kind  employed  must  contain  no  lead. 

Boracic  Acid. — The  native  boracic  acid,  after  fusion  and 
pulverization,  is  to  be  employed  whenever  the  use  of  this  acid 
is  indicated.     It  ought  to  be  kept  in  well-stopped  bottles. 

Boracic  acid  has  the  property  of  forming  with  silica  and 
all  the  bases  very  fusible  compounds,  and  is  from  this  cause 
a  very  universal  flux.  Nevertheless,  there  is  an  inconvenience 
attached  to  its  use;  it  is  very  volatile,  so  that  sometimes  the 
greater  part  employed  in  an  assay  sublimes  before  it  has  had 
time  to  perform  its  office. 


NON-METALLIC  FLUXES.  205 

Borax,  Bihorate  of  Soda,  is  an  excellent  and  nearly  uni- 
versal flux,  because  it  has  the  property  of  forming,  like  boracic 
acid,  fusible  compounds  with  silica  and  nearly  all  the  bases, 
and  is  preferable  to  that  acid  because  it  is  much  less  volatile. 

It  may  be  used  at  a  high  or  low  temperature.  In  the 
first  case,  it  is  employed  in  the  assay  of  gold  and  silver  be- 
cause it  fuses  and  combines  with  most  metallic  oxides,  or  in 
obtaining  a  regulus,  that  is  to  say,  to  separate  the  metals, 
their  arseniurets  and  sulphurets,  from  any  stony  matter  with 
which  they  may  be  mixed,  because  this  salt  is  neither  oxidat- 
ing nor  desulphurating.  In  the  second  case,  it  is  employed 
in  the  assay  of  iron  and  tin  ores,  as  in  the  presence  of  char- 
coal it  retains  but  traces  of  their  oxides,  and,  indeed,  much 
less  than  generally  remains  with  the  silicates. 

When  borax  is  heated  it  fuses  in  its  water  of  crystalliza- 
tion, and  undergoes  an  enormous  increase  of  volume;  at  a 
higher  temperature,  it  fuses  and  forms  a  transparent  glass, 
which  becomes  dull  on  the  surface  by  exposure  to  air.  Only 
the  fused  vitrified  borax  ought  to  be  used  in  assays.  It  must 
be  reduced  to  powder,  and  kept  in  well-closed  vessels. 

Fluor  Spar,  Fluoride  of  Calcium,  is  rarely  employed  in 
assays,  but  in  certain  cases  is  an  excellent  flux,  especially 
where  sulphates  are  present,  with  many  of  which  it  forms 
very  fusible  compounds.  The  best  proportions  are  about 
equal  equivalents  of  the  spar  and  the  anhydrous  sulphates  of 
alkali,  lime,  and  oxide  of  lead :  but  for  the  sulphate  of  baryta, 
two  eqs.  of  the  spar  for  one  eq.  of  the  sulphate. 

It  likewise  assists  in  fluxing  silicates,  partly  by  direct 
union  with  them,  and  partly  by  yielding  fluosilicic  gas,  and 
leaving  lime  to  unite  with  silica. 

Carbonate  of  Potash  and  Carbonate  of  Soda. — It  has 
been  already  proved  that  they  possess  oxidating  and  desul- 
phurating power ;  they  will  now  be  considered  as  fluxes. 

They  are  decomposed  in  the  dry  way  by  silica  and  the 
silicates,  with  the  separation  of  carbonic  acid.  The  presence 
of  charcoal  much  facilitates  this  decomposition. 

The  silicates  of  potassa  and  soda  fuse  readily  and  flow 
freely. 

They  form  fusible  compounds  with  the  greater  part  of  the 
metallic  oxides ;  in  these  combinations  the  oxide  replaces  a 
certain  quantity  of  carbonic  acid ;  but  these  compounds  are 
not  stable,  they  are  decomposed  by  carbon,  which  reduces  the 
oxide,  or  by  water,  which  dissolves  the  alkali. 


206  FLUXES  : — NITRE  ; — SALT. 

On  account  of  their  great  fusibility,  the  alkaline  carbonates 
can  retain  in  suspension,  without  losing  their  fluidity,  a  large 
proportion  of  pulverized  infusible  substances,  as  an  earth, 
charcoal,  &c. 

The  alkaline  carbonates  ought  to  be  deprived  of  their 
water  of  crystallization  for  assaying  purposes ;  in  fact,  it  would 
be  better  to  fuse  them  before  use.  They  must,  in  all  cases, 
be  kept  in  well-stopped  vessels. 

They  may  be  used  indifferently,  but  carbonate  of  soda  is  to 
be  preferred  as  it  does  not  deliquesce. 

A  mixture  of  both  is  far  preferable  to  either  alone,  and 
moreover  requires  a  lower  heat  for  its  fusion.  The  proper 
proportions  are  ten  parts  of  efiloresced  carbonate  of  soda  and 
thirteen  parts  of  dry  carbonate  of  potassa.  The  two  are  to  be 
intimately  incorporated  by  trituration  and  the  mixture  kept  in 
stoppered  bottles.  This  flux  is  the  one  of  most  general  ap- 
plication. 

The  alkaline  carbonates  of  commerce  always  contain  sul- 
phates and  chlorides.  In  ordinary  cases,  this  causes  no  incon- 
venience, but  there  are  circumstances  under  which  the  pre- 
sence of  sulphuric  acid  would  be  injurious. 

Carbonate  of  potash  can  readily  be  procured  free  from 
sulphate  and  chloride  by  means  of  nitre  and  charcoal,  as  fol- 
lows : — Pulverize  roughly  6  parts  of  pure  nitre,  and  mix  them 
with  1  part  of  charcoal ;  then  project  the  mixture  spoonful  by 
spoonful  into  a  red-hot  iron  crucible.  The  projection  of  each 
spoonful  is  accompanied  by  a  vivid  deflagration,  and  car- 
bonate of  potash  is  found  in  a  fused  state  at  the  bottom  of 
the  crucible ;  it  must  be  pulverized,  separated  from  excess  of 
charcoal,  and  kept  in  a  dry  state  for  use. 

Carbonate  of  soda  may  be  obtained  in  much  the  same  way, 
substituting  nitrate  of  soda  for  nitrate  of  potash ;  or  by  re- 
peatedly crystallizing  the  carbonate  of  commerce. 

Nitrate  of  Potash. — The  presence  of  silica  or  silicates  much 
assists  its  decomposition.  It  is  used  as  an  oxidizing  agent, 
the  potash  resulting  from  its  decomposition  acting  as  flux. 
To  prevent  violent  action  and  ejection  of  particles  of  matter, 
its  addition  to  the  crucible  must  be  careful  and  gradual. 
Nitre  is  also  employed  in  some  instances  as  a  substitute 
for  nitrate  of  ammonia  for  effecting  the  rapid  and  perfect 
combustion  of  organic  substances. 

Common  Salt,  Chloride  of  Sodium,  was  much  recommended 


BLACK  FLUX  AND  ITS  EQUIVALENTS.  207 

by  the  older  assayers,  either  mixed  with  flux,  or  a  certain 
quantity  placed  above  it,  for  the  purpose  of  preserving  the 
substances  beneath  from  the  action  of  the  atmosphere,  or  to 
ameliorate  the  action  of  such  bodies  as  cause  much  ebullition. 
It  is  very  useful  in  lead  assays.  When  it  is  used,  it  must  be 
previously  pounded  and  heated  to  dull  redness  in  a  crucible 
to  prevent  its  decrepitation. 

Black  Flux  and  its  Equivalents. — Black  flux  is  both  a  re- 
ducing and  fusing  agent.  It  is  a  mixture  of  carbonate  of 
potash  and  charcoal  in  a  minute  state  of  division.  It  is  much 
employed,  and  very  serviceable.  It  is  prepared  by  mixing  2 
parts  of  argol  with  1  part  of  nitre,  placing  the  mixture  in  an 
iron  vessel  and  setting  it  on  fire  by  a  burning  coal  or  red-hot 
rod.  When  the  combustion  is  finished,  the  substance  is  pul- 
verized and  sifted  whilst  yet  hot,  and  kept  in  well-stopped 
jars,  as  it  rapidly  absorbs  moisture  from  the  atmosphere. 

Black  flux  is  much  used  in  lead  and  copper  assays ;  but  as 
it  boils  up  greatly  at  the  commencement  of  the  operation,  the 
crucible  must  not  be  more  than  two-thirds  full. 

It  can  be  readily  imagined  that,  as  it  fuses  and  reduces  at 
the  same  time,  the  relative  proportions  of  alkaline,  carbonate, 
and  charcoal  ought  to  vary  according  to  the  nature  of  the 
substance  acted  upon ;  and  it  is  often  expedient  to  employ  the 
greatest  possible  proportion  of  alkali  to  obtain  the  largest 
yield  of  metal.  Black  flux  may  be  obtained  richer  in  carbon 
by  mixing  1  part  of  nitre  with  2  J  or  three  parts  of  argol. 

Common  black  flux  contains  5  per  cent,  of  charcoal.  The 
flux  prepared  with  2J  of  tartar  or  argol  to  1  of  nitre,  con- 
tains 8  per  cent.,  and  that  with  3  contains  12  per  cent,  of 
charcoal. 

Black  flux  can  be  replaced  by  anhydrous  or  dry  carbonate 
of  soda  mixed  with  some  reducing  agent.  When  charcoal  is 
employed  it  must  be  reduced  to  a  very  fine  powder ;  in  fact, 
it  ought  to  be  levigated. 

The  three  following  fluxes  are  very  useful  : 

Carbonate  of  Soda  .         .     94     88     816 

Charcoal        .         .         .         .       6     12     184 

The  second  is  very  nearly  equivalent  to  sodium  and  car- 
bonic acid,  and  the  third  to  sodium  and  carbonic  oxide ;  but 
it  must  be  observed,  that  whatever  precautions  be  taken, 
these  mixtures  never  become  so  liquid  as  black  flux,  because 
the  charcoal  tends  very  much  to  separate  and  rise  to  the  sur- 
face. 


208  FLUXES  : — POTASSA  SALTS. 

Instead  of  charcoal,  it  is  preferable  to  use  sugar  or  starch 
to  make  a  flux  equivalent  to  black  flux  with  carbonate  of  soda; 
the  mixture  must  be  made  most  intimately. 

Cream  of  tartar,  carbonized  by  a  semi-combustion  until  it 
is  reduced  to  half  its  weight,  is  a  very  good  substitute  for 
black  flux :  it  contains  about  10  per  cent,  of  charcoal. 

Argol^  Cream  of  Tartar^  Bitartrate  of  Potassa. — When  bi- 
tartrate  of  potassa  is  heated  in  a  covered  crucible,  a  rapid 
decomposition  takes  place,  accompanied  by  a  disengagement 
of  inflammable  gases ;  the  substance  agglomerates,  but  with- 
out fusing  or  boiling  up.  The  residue  is  black,  blebby,  and 
friable,  and  contains  15  per  cent,  of  carbon  when  produced 
from  rough  tartar  or  argol,  and  7  per  cent,  from  cream  of 
tartar. 

These  reagents  produce  the  same  effects  as  black  flux,  and 
possess  more  reducing  power,  because  they  contain  more  com- 
bustible matter;  but  this  is  an  inconvenience,  because  the 
excess  prevents  their  entering  into  full  fusion  when  the 
substance  to  be  assayed  requires  but  a  small  proportion  of  a 
reducing  agent.  They  can  be  used  with  success  in  assays  re- 
quiring much  carbonaceous  matter. 

Bisulphate  of  Potassa  is  a  convenient  flux  for  several 
minerals,  such  as  for  those  highly  aluminous  {Hose),  for  chromic 
and  other  similar  ores  (Booth). 

Salt  of  Sorrel,  Binoxalate  of  Potassa,  when  heated  is  de- 
composed. It  decrepitates  feebly,  and  during  its  decomposi- 
tion is  covered  with  a  blue  flame ;  it  at  first  softens,  and  when 
fully  fused,  is  wholly  converted  into  carbonate.  When  the 
oxalate  is  very  pure,  the  resulting  carbonate  is  perfectly  white 
and  free  from  charcoal ;  but  very  often  it  is  spotted  with 
blackish  marks.     It  has  no  very  great  reducing  power. 

Cyanide  of  Potassium  acts  powerfully  both  as  a  reducing 
and  desulphurizing  reagent,  and  is  a  very  useful  flux  in  small 
assays.  According  to  Liebig  it  has  the  advantage  over  the 
potassa  salts  with  vegetable  acids,  of  not  carbonizing  the 
metal,  for  the  salt  changes  at  the  expense  of  the  metallic 
oxide  into  cyanate  of  potassa.  If  the  metallic  oxide  predomi- 
nates, the  rest  will  be  reduced  by  the  cyanic  acid  without 
separation  of  carbon. 

White,  or  Mottled  Soap  is  a  compound  of  soda  with  a  fat 
acid.  When  heated  in  close  vessels  it  fuses,  boiling  up  con- 
siderably, and  during  its  decomposition  gives  off  smoke  and 


METALLIC  FLUXES  : — LITHARGE  ; — GLASS.  209 

combustible  gases,  and  leaves  a  residue  composed  of  car- 
bonate of  soda  with  about  5  per  cent,  of  charcoal.  Of  all 
reducing  agents  soap  absorbs  the  greatest  quantity  of  oxygen, 
and  as  the  residue  of  its  decomposition  by  heat  affords  but 
little  charcoal,  it  has  the  property  of  forming  very  fluid  slags. 
Nevertheless,  it  is  rarely  employed  because  certain  inconve- 
niences outweigh  its  advantages.  These  inconveniences  are, 
its  bubbling  up  and  its  extreme  lightness.  It  also  requires  to 
be  rasped,  in  order  to  mix  it  perfectly  with  the  substances  it 
is  to  decompose,  and  it  then  occupies  a  very  large  volume, 
and  requires  correspondingly  large  crucibles.  There  are 
nevertheless  cases  where  it  may  be  used  with  advantage  by 
mixing  it  with  other  fluxes. 

All  those  fluxes  containing  alkaline  and  carbonaceous  sub- 
stances are  reducing  and  desulphurizing,  besides  acting  as 
fluxes,  properly  so  called ;  they  also  produce  another  efi'ect 
w^hich  it  is  useful  to  know,  viz  :  they  have  the  property  of  in- 
troducing a  certain  quantity  of  potassium  or  sodium  into  the 
reduced  metal.  This  was  first  pointed  out  by  M.  Vauquelin.* 
He  found  that  when  oxide  of  antimony,  bismuth,  or  lead  was 
fused  with  an  excess  of  tartar,  the  metals  obtained  possessed 
some  peculiar  characters,  which  they  owed  to  the  presence  of 
several  per  cent,  of  potassium. 

Metallic  Fluxes — Litharge  and  Ceruse, — These  bodies 
always  act  as  fluxes,  but  at  the  same  time  often  produce  an 
alloy  with  the  metal  contained  in  the  ore  to  be  assayed. 
Ceruse  produces  the  same  fluxing  efiect  as  litharge.  The 
litharge  is  the  better  flux,  and  is  very  useful  in  a  great  number 
of  assays. 

It  fuses  readily  with  the  oxides  of  iron,  copper,  bismuth, 
antimony  and  arsenic,  sulphate  of  lead  and  the  silicates,  in 
the  proportion  of  2  to  5  parts  of  litharge  to  1  part  of  the 
substance  to  be  fluxed ;  other  oxides  require  a  larger  amount 
of  litharge.  Its  action  is  that  of  promoting  fusion,  reducing 
an  oxide  and  desulphurizing  a  sulphuret. 

Glass  of  Lead,  Silicate  of  Lead. — The  silicates  of  lead  are 
preferable  to  litharge  in  the  treatment  of  substances  contain- 
ing no  silica,  or  which  contain  earths  or  oxides  not  capable  of 
forming  a  compound  with  oxide  of  lead,  excepting  by  the  aid 
of  silica.     It  may  be  made  by  fusing  1  part  of  sand  with  4 

*  Annales  des  Mines. 


210  FLUXING : — CALCINATION. 

parts  of  litharge ;  if  required  more  fusible,  a  larger  proportion 
of  litharge  must  be  added. 

Borates  of  Lead. — The  borates  of  lead  are  better  fluxes 
than  the  silicates  when  the  substance  to  be  assayed  contains 
free  earths ;  but  in  order  to  prevent  them  swelling  up  much 
when  fused,  they  must  contain  an  excess  of  oxide  of  lead. 
The  borate  of  lead  containing  .9056  of  oxide  of  lead  and  .0944 
of  boracic  acid,  is  very  good.  Instead  of  borate  of  lead,  a 
mixture  of  fused  borax  and  litharge  may  be  employed ;  it  is 
equally  serviceable. 

Sulphate  of  Lead  is  decomposed  by  all  silicious  matters 
and  by  lime,  so  that  when  these  substances  are  present  litharge 
is  produced,  which  fluxes  them. 

Oxide  of  Copper  is  rarely  used  as  a  flux  for  oxidated  mat- 
ters, but  is  sometimes  employed  in  the  assays  of  gold  and  zinc 
to  form  an  alloy  with  those  metals.  In  this  case  a  reducing 
flux  must  be  mixed  with  the  oxide.  Metallic  copper  may  be 
used,  but  is  not  so  useful,  as  it  cannot  be  so  intimately  mixed 
with  the  assay. 

Oxides  of  Iron  are  good  fluxes  for  the  silicates.  They  are, 
however,  rarely  employed  for  that  purpose ;  they  are  more 
often  used  to  introduce  metallic  iron  into  an  alloy  to  collect 
an  infusible,  or  nearly  infusible  metal,  by  alloying  it  with 
iron,  such  as  manganese,  tungsten,  or  molybdenum. 

Calcination. — The  separation  (in  a  dry  way)  of  volatile 
from  fixed  matter,  by  heat,  is  termed  calcination.  The  pro- 
cess is  applicable 

To  the  expulsion  of  water  from  salts,  minerals,  coals  and 
other  substances. 

"  "  "    carbonic  acid  from  certain  carbonates.  ^ 

"  "  "    arsenic  and  sulphur  from  cobalt,  nickel 

and  other  sulphuretted  compounds. 

"  "  "    bituminous  matter  from  coals,  and  cer- 

tain minerals  and  ores. 
To  the  ignition  of  quartz  and  silicious  minerals  to  promote 

their  disintegration  (p.  77). 
For  the  purpose  of  expelling  the  combined  water  of  argilla- 
ceous minerals,  and  of  thus  rendering  them  more  obstinate 

to  the  solvent  action  of  acids  and  reagents. 

If  the  substance  under  process  is  organic,  its  calcination  in 
a  close  vessel  by  a  medium  heat  usually  effects  only  partial 
decomposition,  the  gaseous  matter  generated  escaping  through 
interstices  and  the  fixed  components  remaining  with  a  portion 


COKING. — INCINERATION. — ROASTING.  211 

of  unaltered  carbon.  Performed  in  this  manner,  the  process 
takes  the  name  of  coking,  familiar  instances  of  which  are  the 
formation  of  coke  by  distilling  coal  in  closed  retorts,  the 
manufacture  of  charcoal  from  wood,  and  of  bone  black  from 
bones. 

By  increasing  the  temperature  and  admitting  the  air,  the 
whole  of  the  alterable  and  volatile  matter  is  expelled,  the 
fixed  matter  remaining  as  ashes.  The  process  is  then  styled 
incineration,  and  in  this  way  the  coke,  charcoal  and  ivory 
black,  obtained  as  above  directed,  may  be  entirely  reduced 
to  their  incombustible  portions  or  ashes. 

Calcination  is  effected  in  platinum  spoons  or  crucibles,  in 
delicate  experiments,  over  a  spirit  lamp ;  but  in  large  opera- 
tions a  furnace  is  required,  and  the  containing  vessels  are 
crucibles  of  either  metal  or  earthenware,  according  to  the 
nature  of  the  substance  to  be  heated,  though  the  latter  are 
often  unsuitable  for  temperatures  above  a  red  heat. 

When  the  operation  is  finished,  the  crucible  should  be  taken 
from  the  fire  and  allowed  to  cool  gradually.  The  cover  is 
then  to  be  lifted  oif  and  the  contents  taken  out  with  a  spatula, 
and  the  portions  adhering  to  the  sides  removed  with  a  feather. 

If  the  substance  undergoing  calcination  is  fusible,  it  is 
necessary  when  quantities  are  to  be  ascertained,  to  weigh  both 
the  crucible  and  contents  before  ignition,  so  that  the  amount 
of  volatile  matter  driven  off  may  be  expressed  by  the  weight 
lost  in  heating.  Water  alone  or  acidulated,  with  the  aid  of 
heat  generally  removes  the  calcined  matter  from  the  crucible. 

A  body  decrepitating  by  heat  should  be  powdered  before 
being  subjected  to  the  process  of  calcination,  and  the  tem- 
perature should  be  raised  slowly  and  gradually,  otherwise 
when  the  crucible  is  not  covered,  a  loss  may  result  from  the 
ejection  of  particles. 

To  avoid  contact  with  the  generated  vapors  or  with  the 
atmosphere,  which  to  some  substances  act  as  reducing  agents, 
the  crucible  should  in  such  cases  be  covered,  and  if  tightly 
luted  perforated  with  one  or  more  small  holes  for  the  escape 
of  vapor. 

Roasting  (as  the  term  is  generally  used)  is  a  kind  of  cal- 
cination to  which  many  ores  are  submitted  before  their  final 
reduction  to  the  metallic  state,  for  the  purpose  of  expelling 
ingredients  which  would  either  delay  that  process  or  be  in- 
jurious to  the  metal  when  extracted.     In  this  way  water, 


212  ROASTING.— DEFLAGRATION. 

carbonic  acid,  sulphur,  selenium,  arsenic,  and  sometimes  other 
substances,  are  driven  off  from  the  ores  containing  them. 
The  term  is  also  applied  to  other  processes,  among  the  most 
important  of  which  is  that  of  the  exposure  to  heat  and  air  by 
which  metals  become  altered  in  composition.  Thus,  copper 
becomes  oxidized,  and  antimony  and  arsenic  acidified  by 
union  with  oxygen. 

Roasting  is  always  effected  in  broad,  shallow  open  vessels, 
so  that  the  air  may  have  free  access ;  and  in  order  to  promote 
the  absorption  of  oxygen  or  the  escape  of  the  volatile  sab- 
stance,  the  surface  of  the  body  to  be  heated  should  be  in- 
creased by  previous  pulverization,  and  it  should  ba  constantly 
stirred  during  the  operation  so  as  to  present  as  many  points 
of  contact  as  possible.  The  most  suitable  vessel  is  a  baked 
earthenware  saucer  or  capsule  placed  in  a  muffle  or  upon  the 
bars  of  a  calcining  furnace.  Sometimes  a  crucible  is  used, 
and  then  the  position  of  the  vessel  in  the  furnace  should  be 
slightly  inclined  on  one  side.  In  either  case  the  vessels 
should  be  heated  to  dull  redness  previous  to  receiving  their 
charge. 

That  species  of  roasting  termed  deflagration  is  effected 
by  rapidly  heating  the  substance  to  be  oxidized,  together 
with  some  additional  body  as  an  oxidizing  agent,  as  a 
nitrate  or  chlorate  for  instance.  The  powdered  mixture  is 
added  portionwise  to  the  crucible  previously  heated,  and 
maintained  at  redness  during  the  operation.  The  vivid  and 
sudden  combustion  which  ensues  modifies  the  composition  of 
the  original  substance  and  increases  its  amount  of  oxygen  at 
the  expense  of  the  addendum.  Thus  for  instance,  sulphuret 
of  arsenic  is  deflagrated  with  nitre  to  produce  arseniate  of 
potassa,  titanium  and  certain  other  metals  to  be  transformed 
into  oxides. 

Deflagration  is  also  used  as  a  means  of  detecting  the  pre- 
sence of  nitric  or  chloric  acids.  For  this  purpose  the  sus- 
pected substance  is  to  be  heated  with  cyanide  of  potassium, 
in  a  small  platinum  spoon.  If  deflagration  ensues  it  is  a  test 
of  the  presence  of  one  of  them,  or  a  compound  of  one  of  them. 

The  crucibles  may  be  of  clay  or  metal  according  to  the 
nature  of  the  substance  to  be  heated.  The  roasting  of  sub- 
stances for  the  expulsion  of  organic  matter  may  be  effected 
in  platinum  vessels,  provided  the  heat  is  not  carried  suffi- 
ciently high  to  produce  fusion  of  the  substance  being  roasted. 


DECREPITATION. — REDUCTION.  218 

The  heat  must,  at  first,  be  very  gradually  applied,  and  at 
no  time  be  made  great  enough  to  fuse  or  agglutinate  the  ma- 
terial, otherwise  the  process  will  have  to  be  suspended  in  order 
to  repulverize  the  matter.  Proper  care  at  the  commencement 
will  obviate  the  necessity  of  this  additional  trouble.  When 
the  heat  has  been  cautiously  raised  to  redness  and  all  liability 
of  fusion  is  over,  the  fire  may  be  urged  to  the  production  of 
a  yellowish  red  or  even  white  heat,  so  that  the  expulsion  of 
volatile  matter  may  be  complete. 

Roasting  operations  which  disengage  deleterious  or  disa- 
greeable fumes  should  be  carried  on  in  the  open  air  or  under  a 
hood,  and  when  the  volatile  matters  are  valuable  they  may 
be  condensed  as  directed  in  distillation  and  sublimation. 

Decrepitation,  which  frequently  occurs  sftid  occasions  loss 
by  ejections  of  particles  of  the  mixture,  is  owing  to  the  sudden 
vaporization  of  the  water  of  crystallization,  which  in  finding 
vent  scatters  the  confining  substance  with  a  crackling  noise. 
To  prevent  this  loss,  the  crucible  should  be  loosely  covered 
until  decrepitation  ceases. 

Reduction. — This  operation  is  employed  for  the  separation 
of  metallic  bases  from  any  bodies  with  which  they  are  com- 
bined ;  but  is  generally  confined  to  the  extraction  from  an 
oxide — that  being  the  kind  of  combination  most  commonly 
met  with.  The  combined  action  of  heat  and  certain  reagents 
is  required  to  efi'ect  this  result,  the  temperature  varying  with 
the  nature  of  the  substance  to  be  reduced. 

The  most  usual  reducing  agents  are  charcoal  and  hydrogen 
gas.  Tallow,  oil  and  resin  are  sometimes  used,  but  being 
easily  decomposed  they  are  dissipated  before  entire  reduction 
has  occurred.  Sugar  and  starch  are  also  occasionally  em- 
ployed. We  shall,  however,  confine  our  remarks  to  the  two 
principal  articles. 

Reduction  hy  Qharcoal. — Charcoal  is  used  for  this  purpose 
in  two  ways,  either  in  powder  and  directly  mixed  with  the 
substance,  or  as  a  lining  coat  to  the  crucible  in  which  the 
reduction  is  accomplished.  The  first  mode  is  objectionable, 
because  the  excess  of  coal  which  is  required  to  be  used  inter- 
feres with  the  agglomeration  of  the  particles  of  reduced  metal. 
Whenever  it  is  adopted,  the  quantity  of  coal  dust  to  be  added, 
which  must  be  sufficient  to  transform  all  the  oxygen  of  the 
oxide  into  carbonic  acid,  can  be  determined  by  calculation. 
This  amount  is  then  mixed  thoroughly  with  the  oxide  pre- 


214  REDUCTION  BY  HYDROGEN. 

viously  powdered,  and  is  transferred  to  a  crucible,  taking  care 
to  place  the  charge  in  the  centre  and  to  cover  the  contents 
with  a  layer  of  the  dust.  The  whole  is  then  to  be  subjected 
to  the  heat  of  a  furnace,  assisted  if  necessary,  by  a  blast. 
The  reduction  in  this  way,  the  most  convenient  for  large 
quantities,  is  rapid  and  complete,  but  the  metallic  residue  is 
often  mixed  with  coal  dust. 

In  general  the  mere  contact  of  carbon  is  sufficient  to  eifect 
reduction,  and  consequently  the  inconvenience  of  the  above 
plan  may  be  avoided  by  the  use  of  a  brasque  or  crucible  lined 
interiorly  with  charcoal.  An  earthen  crucible  is  very  readily 
brasqued  as  follows : — A  mixture  of  three  parts  of  charcoal 
dust,  and  two  parts  of  powdered  clay,  is  mixed  with  water  and 
kneaded  into  a  plastic  dough.  The  bottom  of  the  crucible  is 
then  covered  with  this  dough,  and  a  wooden  cylindrical  core 
of  diameter  equal  to  that  required  for  the  cavity,  is  inserted 
in  the  centre  and  surrounded  with  more  of  the  same  dough, 
which  is  compressed  with  the  fingers  at  each  addition  so  as  to 
make  the  whole  as  compact  as  possible.  The  core  is  then  to 
be  carefully  withdrawn,  and  the  crucible  placed  aside  to  dry. 
A  platinum  crucible,  which  is  as  applicable  as  clay  for  certain 
operations,  can  be  brasqued  in  the  same  way.  Some  operators 
use  the  coal  dust  without  clay,  and  moisten  it  with  water  or 
oil.  The  crucibles  should  be  free  from  external  fissures  to 
prevent  access  of  air,  and  must  always  be  covered  when 
heated.  The  reduction  by  this  plan  is  slower  than  by  the 
first  mode,  and  requires  a  higher  temperature,  but  the  metal 
as  procured  is  cleaner. 

The  powdered  oxide  is  placed  in  the  cavity  in  sufficient 
quantity  to  fill  it,  then  compressed  with  the  fingers  and  co- 
vered with  a  layer  of  coal  dust.  The  cover  being  luted  upon 
the  crucible  the  whole  is  to  be  heated  in  a  blast  furnace.  The 
reduction  proceeds  from  the  surface,  that  part  of  the  oxide  next 
to  the  charcoal  being  first  acted  upon.  The  time  required  de- 
pends upon  the  nature  of  the  oxide,  the  degree  of  tempera- 
ture and  the  quantity  under  process :  sometimes,  particularly 
when  the  metals  are  very  fusible,  the  reduced  particles  collect 
in  a  clean  lump  at  the  bottom  of  the  crucible,  and  are  easily 
removable  when  cold,  with  the  finger  or  spatula.  Others 
again,  more  refractory,  form  a  very  friable  lump  of  metallic 
powder. 

Reduction  hy  Hydrogen. — This  mode,  which  is  much  used  in 


REDUCTION  APPARATUS. 


215 


analyses,  consists  in  passing  a  current  of  hydrogen  gas  over  the 
metallic  oxides  heated  to  redness  in  a  glass,  or  better,  por- 
celain tube,  and  is  equally  applicable  to  some  chlorides  and 
other  compounds.  The  arrangement  of  the  requsite  appa- 
ratus is  shown  in  Fig.  166.     ^  is  a  flask  for  the  disengage- 

Fig.  166. 


ment  of  hydrogen  gas,  by  the  action  of  dilute  sulphuric  acid 
upon  zinc,  the  funneled  tube  a  being  for  the  ingress  of  the 
acid.  The  disengagement  tube  h  is  bent  at  right  angles  and 
bulbed  midway  in  its  horizontal  arm.  The  bulb  is  to  be  fur- 
nished with  a  plug  of  raw  cotton  for  the  condensation  and 
retention  of  any  aqueous  vapor  that  may  pass  over.  This 
tube  is  joined  hermetically  to  another  short  tube  c  by  means 
of  an  India  rubber  connection.*     The  connecting  tube  is  made 

•  The  use  of  India  rubber  as  a  material  for  forming  flexible  joints  is  one  of 
the  most  important  aids  in  chemical  manipulation,  as  is  shown  by  a  reference 
to  many  pieces  of  apparatus.  Its  property  of  readily  uniting  at  freshly  cut  sur- 
faces, its  flexibility,  its  ready  and  close  adhesion  to  surfaces,  and  power  of  resist- 
ing the  action  of  corrosive  vapors  except  those  of  chlorine,  sulphuric  and  nitric 
acids  and  a  few  others,  render  it  peculiarly  excellent  for  many  mechanical  purposes 
of  the  laboratory.  Tubes  of  any  shape  and  size,  according  to  the  form  and  dimen- 
sions of  the  parts  of  apparatus  to  be  connected,  are  to  be  fashioned  out  of  it  with 
almost  equal  flicility.  For  the  transmission  of  corrosive  vapors  or  gases  they  should, 
have  an  outer  layer,  the  seam  in  which  must  be  directly  opposite  to  that  in  the  tube 
which  it  invests,  so  as  to  ensure  perfect  tightness.  Prof.  Booth  uses  the  India 
rubber  pipe,  made  by  Goodyear  as  conduits  for  steam  in  boiling  corrosive  liquids 


216  FLEXIBLE  TUBES. — GAS  BAGS. 

of  sheet  caoutcliouc  about  one-twelfth  of  an  inch  in  thickness. 

A  piece  of  the  required  length  of 
^ig-  16'''-  the  tube  and  twice  the  intended 

width  is  cut  out  and  wrapped 
around  a  cylindrical  glass  rod,  c?, 
Fig.  167,  of  diameter  very  nearly 
as  great  as  that  for  the  tube  to 
be  formed.  The  ends  are  then 
brought  closely  together  by  com- 
pression between  the  thumb  and 
fingers  as  at  a,  and  the  excess 
removed,  close  to  the  surface  of  the  rod,  with  a  pair  of 
clean  sharp  scissors.  The  freshly  cut  edges  being  further 
pinched  together  throughout  the  length  of  the  tube,  form  a 
close,  air-tight,  scarcely  perceptible  joint.  The  rod  is  then 
to  be  withdrawn  and  the  tube  thus  formed  carefully  drawn  over 
the  end  of  one  of  the  glass  tubes  to  be  connected,  so  as  to  form 
an  extension  for  the  reception  of  the  end  of  the  other.  The  two 
ends  should  approach  each  other  almost  to  contact,  a  minute 
interval  being  necessary  to  afford  the  necessary  flexibility. 
This  junction  pipe  is  fastened  to  the  surface  of  the  tube  by 
fine  twine  wrapped  or  tied  around  each  of  its  ends,  as  shown 
at  X,  Fig.  166. 

The  gas  bottle  thus  fitted  is  connected,  by  means  of  a  per- 
forated cork  with  the  drying  tube  c?,  filled  with  lumps  of  dried 
chloride  of  calcium.     At  the  opposite  end  of  the  drying  tube 

by  that  agent,  and  gives  it  consistence  with  flexible  lead  pipe,  which  he  covers 
externally  and  internally.  A  better  frame  work  would  be  a  spiral  coil  of  wire. 
The  tubing  made  of  canvas  imbued  with  caoutchouc  is  less  durable,  and  does 
not  admit  of  such  general  application. 

Before  forming  the  tube  above  mentioned,  it  is  better  to  warm  the  caoutchouc, 
by  which  its  flexibility  is  increased  and  its  cut  surface  made  to  adhere  more  rea- 
dily and  closely.  The  scissors  cut  more  freely  when  previously  moistened. 
These  flexible  joints  not  only  relieve  the  apparatus  of  stifiness  and  consequent 
liability  to  fracture,  but  enable  the  operator  to  adjust  it  more  rapidly  and  satis- 
factorily than  he  could  possibly  do  without  them.  A  little  practice  upon  shreds 
will  give  great  proficiency  in  the  art  of  forming  India  rubber  tubes  and  joints. 

India  rubber  for  this  purpose  is  now  made  by  Goodyear,  New  York,  who  sells 
it  in  sheets  of  various  sizes.  Gas  bags  are  also  made  of  caoutchouc.  The  larger 
sized,  pp.  171,  173,  are  to  be  procured  from  the  manufacturer.  Smaller  ones, 
for  nice  purposes,  may  be  readily  made  from  the  rubber  bottles  of  the  shops. 
One  of  uniform  thickness,  and  as  free  as  possible  from  indentations  and  imper- 
fections, is  softened  in  boiling  water  or  by  exposure  for  several  hours  to  the 
vapor  of  ether,  and  then  adjusted  upon  a  stop-cock  with  a  syringe  attached.  The 
air  is  then  to  be  injected  slowly  so  that  the  expansion  of  the  bag  may  be  gradual 
and  uniform  throughout  all  its  pans. 


REDUCTION  BY  HYDROGEN.  217 

e,  is  another  tube  with  a  bulb  blown  in  its  centre  for  the  recep- 
tion of  the  substance  to  be  reduced,  and  in  which  it  is  heated 
by  the  flame  of  a  spirit  lamp.  This  tube,  like  the  other,  is 
annexed  by  elastic  joints  to  the  short  tube  connected  with 
the  desiccating  tube  through  a  perforated  cork. 

This  plan,  first  proposed  by  Berzelius,  was  used  by  him  in 
the  synthesis  of  water,  binoxide  of  copper  being  the  substance 
employed  to  abstract  the  hydrogen,  its  oxygen  forming  water 
therewith. 

Hydrogen  is  a  powerful  reducing  agent,  and  leaves  the 
metal  absolutely  pure.  At  a  red  or  white  heat,  its  action  will 
reduce  the  oxides  of  lead,  bismuth,  copper,  antimony,  zinc, 
iron,  cobalt,  nickel,  tungsten,  molybdenum,  and  uranium. 

The  heat  should  not  be  applied  to  the  bulb  until  it  is  entirely 
freed  from  air,  which  may  be  done  by  allowing  the  hydrogen  to 
pass  over  some  minutes  previously.  A  disregard  of  this  pre- 
caution may  cause  an  explosion  from  the  combustion  of  a 
mixture  of  hydrogen  and  atmospheric  air. 

The  above  apparatus  answers  very  well  for  decomposing 
metallic  sulphurets  by  chlorine.  It  is  also  applicable  for 
heating  solids  in  gases,  and  serves  for  the  preparation  of 
chloride  of  sulphur,  of  phosphorus,  and  of  many  other  vola- 
tile chlorides.  For  this  purpose  it  is  only  necessary  to  replace 
the  flask  A  by  other  suitable  generating  vessels,  and  the 
extreme  end  of  the  exit  tube  by  a  tubulated  retort  with  its 
beak  bent  downwards  and  leading  into  the  recipient,  kept 
cool  by  a  frigorific  mixture. 

The  tubes  for  these  purposes  must  be  of  hard  glass  and 
entirely  free  from  lead,  and  not  exceeding  a  third  of  an  inch 
in  width.  The  bulbs  should  be  of  IJ  inch  diameter.  The 
chlorcalcium  tube  may  be  three-fourths  of  an  inch  wide. 

There  are  other  modes  of  reduction  of  less  general  applica- 
tion, however,  than  the  preceding.  Metals  may  be  precipi- 
tated in  a  free  state,  in  some  instances,  from  solutions,  by 
presenting  bodies  for  which  their  oxygen  has  a  stronger  affi- 
nity, thus,  for  example,  protosulphate  of  iron  precipitates 
metallic  gold;  phosphorous  acid  mercury;  and  formic  acid  or 
formate  of  soda,  both  of  these  metals,  and  also  silver  and 
platinum,  if  the  liquids  containing  them  in  solution  are  boiled. 
So  also  one  metal  may  reduce  another  if  the  affinity  of  the 
first  for  oxygen  is  greater  than  that  of  the  last.  Thus  me- 
15 


218  REDUCTION  BY  CARBONIC  OXIDE. 

tallic  copper  throws  down  mercury,  silver,  and  arsenic  from 
their  solutions,  and  iron  precipitates  copper. 

Metals  are  also  reduced  by  galvanic  action,  practical  illus- 
trations of  which  are  seen  in  the  galvanoplastic  art.  All 
oxides  which  resist  the  combinedi  action  of  heat  and  charcoal 
or  hydrogen,  are  reduced  by  the^agency  of  galvanism. 

Reduction  by  Carbonic  Oxide. — Another  convenient  agent 
of  reduction,  employed  in  the  same  manner  as  hydrogen,  is 
carbonic  oxide,  made  on  a  small  scale  by  the  action  of  oil  of 
vitriol  on  oxalic  acid,  and  separation  of  the  carbonic  acid 
produced  at  the  same  time,  by  milk  of  lime.  It  readily  re- 
duces the  metallic  oxides  of  nickel,  iron,  zinc,  that  of  lead  at 
a  very  low  temperature,  and  that  of  copper" below  a  red  heat. 
For  heating  in  manufacturing  processes,  it  is  made  by  regu- 
lating the  admission  of  air  to  a  deep  bed  of  ignited  anthracite 
or  other  coals,  and  driving  a  blast  of  air  horizontally  through 
the  gas  as  it  issues  from  the  fire,  all  other  access  of  air  being 
prevented.  It  has  in  this  manner  been  applied  to  re-heating 
and  puddling  furnaces.  Carbonic  oxide  is  doubtless  the  great 
reducing  agent  in  large  metallurgic  operations. 

lioasting  and  Heduction  in  Tubes. — In  very  delicate  ex- 
periments, and  particularly  when  the  volatile  matter  expelled 
by  the  heat  is  to  be  collected  for  examinatio|ji,  roasting  and 
reduction  are  effected  in  small  glass  tubes*  closed  at  one  end. 

*  Porcelain  and  Metallic  Tubes. — For  the  reduction  of  some  oxides  by  contact 
with  gases  at  furnace  temperature,  for  the  decomposition  of  certain  organic  mat- 
ters, such  as  oils,  &c.,  and  for  efF^cting  many  combinations  of  gases  with  soUds, 
the  glass  tubes  are  replaced  by  those  of  porcelain,  iron,  or  platinum. 

Porcelain  tubing  should  be  selected  with  care.  It  should  be  straight,  perfectly 
cylindrical,  Iree  from  defects,  glazed  internally  and  as  thin  as  possible.  These 
tubes  are  adjusted  in  manner  as  directed  for  those  of  glass,  and  heated  over  the 
furnace,  Fig.  103,  but  as  they  are  not  refractory,  care  must  be  taken  in  heating 
them.  It  is  advisable  to  give  them  an  exterior  coaling  of  fire  lute  and  then  dry 
them.  Tlie  fire  should  be  ignited  and  all  moisture  expelled  from  the  charcoal 
before  they  are  placed  in  the  furnace,  otherwise  their  fracture  may  result.  It  is 
indispensable,  too,  that  the  heat  shall  be  carefully  managed,  and  after  the  com- 
l)letion  of  the  process  the  tube  must  not  be  removed  from  the  furnace  until  it 
has  entirely  but  gradually  cooled. 

Iron  tubes  are  used  for  the  decomposition  of  water,  potassa  and  for  other 
operations  to  which  those  of  glass  and  porcelain  are  not  adapted  by  reason  of 
inability  to  withstand  high  heat.     Gas  tubing  is  the  most  economical,  and  can 


ROASTING  AND  REDUCTION  IN  TUBES. 

Fig.  168. 


219 


3 

3  * 


O    5 


The  glass  must  be  white,  difficultly  fusible,  and  free  from  lead. 
The  substance  is  placed  in  the  lower  or  closed  end  of  the  tube, 

be  had  of  all  lengths  and  diameters.     These  also  should  be  covered  exteriorly 
with  luting  so  as  to  prevent  the  oxidation  of  the  iron  by  the  fire. 

Metallic  tubes  of  small  size  may  be  heated  over  the  furnace,  Fig.  103,  but 
those  of  larger  dimensions  require  the  use  of  the  furnace,  Fig.  88.  The  circular 
openings  x  a;,  in  each  side,  are  especially  for  the  passage  of  a  tube.  The  grate 
should  be  elevated  so  that  the  fire  may  entirely  surround  it. 

Metallic  tubes  are  adjusted  to  generating  and  other  apparatus  by  means  of 
metallic  couplings,  gallows  screws,  or,  in  some  cases,  by  fire  lute.  This  latter 
does  not  make  a  secure  or  tight  joint,  and  is  only  used  in  the  absence  of  more 
convenient  means.  The  ends  of  the  tube  should  project  far  enough  beyond  the 
sides  of  the  furnace  to  allow  their  refrigeration  when  necessary.  The  gas  may 
be  introduced  directly  from  the  generating  vessel,  or  from  a  caoutchouc  bag,  or 
gasometer,  merely  by  adjusting  the  end  of  the  tube  with  the  mouth  or  outlet  by 
a  suitable  coupling.  The  resultant  product  may,  in  like  manner,  be  collected  by 
similar  adaptations  to  the  other  end. 

Fragments  of  flint  or  coils  of  iron  or  of  platinum  wire,  placed  within  the  tube, 
increase  the  points  of  contact  of  the  contained  matter  and  greatly  promote  its 
heating. 

As  short  tubes  are  occasionally  used  for  effecting  the  combination  of  substances 
alterable  by  exposure  in  a  hot  state,  they  should,  for  such  purposes,  be  fitted  at 
the  ends  with  screw  plugs  to  prevent  access  of  air. 

Platinum  tubes  are  only  used  on  rare  occasions  for  particular  purposes  to 
which  those  of  glass,  porcelain,  or  iron  are  inapplicable. 


220  ROASTING  AND  REDUCTION  IN  TUBES. 

whicli  is  then  inclined  and  heated  over  the  spirit  lamp,  as  shown 
in  Fig.  174.  In  this  way  sulphur  and  arsenic  may  he  sublimed 
from  certain  of  their  compounds,  and  mercury  from  less  vola- 
tile metals.  By  leaving  the  tube  open  at  both  ends  so  as  to 
allow  free  access  of  air,  many  volatile  bodies  are  oxidized  and 
collect,  on  congelation,  in  the  upper  part  of  the  vessel.  Those 
tubes  with  a  bulb  blown  at  their  lower  end,  as  shown  at  1,  5, 
in  Fig.  168,  are  most  applicable  for  decrepitating  substances. 

Below  are  the  several  forms  of  tubes  used  for  the  reduction 
of  metals,  and  particularly  the  separation  of  arsenic  and  mer- 
cury from  more  fixed  matter.  Any  of  these  forms,  or  even  a 
small  test  tube  4  will  answer.  Berzelius  prefers  the  shape 
of  1 ;  Rose  that  of  2 ;  Liebig  that  of  3 ;  and  Clarke  that  of  5. 

The  letters  a  b  e  in  2,  and  b  in  3,  indicate  the  position  of 
the  substance  to  be  roasted  together  with  its  reducing  agent, 
and  d  and  a  in  2  and  3,  the  rings  of  condensed  volatile 
matter  sublimed  by  the  heat.  Berzelius  and  Rose's,  and 
Liebig's  tubes  are  three  inches  in  length;  Clark's  two  inches. 
Their  diameters  vary  from  -jJgth  to  a  Jth  of  an  inch  according 
to  the  amount  of  substance  to  be  heated. 


CHAPTER    XVI. 

CUPELLATION. 


Gold  and  silver  are  assayed  by  the  agency  of  heat  and 
litharge  in  shallow,  slightly  conical  crucibles.  Fig.  169,  called 
cupels.  This  process  aifords  these  metals  free  from  any  de- 
basement with  which  they  may  be  contaminated;  for,  when 


Fig.  1G9. 


the  alloy  is  heated  together  with  litharge,  all  but  the  precious 
metals  are  oxidized;  and  the  oxides  thus  formed,  together 
with  the  semi-vitrous  litharge,  are  absorbed  by  the  cupel 
whilst  the  nobler  metal  remains  as  a  button  of  absolute 
purity. 


CUPELLATION  : — CUPELS.  221 

Cupels. — Thej  are  generally  made  of  bone  ash,  because 
that  material  fulfils  better  than  any  other  the  necessary  require- 
ments. It  is  resistant  to  the  action  of  the  fused  oxides  of  lead 
and  bismuth,  and  by  its  porosity  facilitates  the  penetration  of 
the  oxides,  and  at  the  same  time  is,  when  made  into  shape, 
strong  enough  to  bear  handling  without  fracture.  The  cupels 
used  at  the  mint  in  this  city,  are  made  in  a  matrix  of  If 
inches  diameter.  The  semi-circular  cavity  is  two-fifths  of  an 
inch  deep  in  the  centre.  This  size,  however,  can  be  varied  and 
they  may  be  made  smaller  or  larger  according  to  the  quantity 
of  matter  to  be  operated  upon.  Their  mode  of  manufacture 
is  as  follows : — Take  bones  or  bone  black  and  calcine  them  in 
an  open  crucible  until  the  expulsion  of  all  animal  and  carbo- 
naceous matter,  which  is  known  by  the  residue  assuming  a 
whitish  appearance.  Empty  the  cooled  contents  of  the  cru- 
cible into  clean  water,  and  give  it  repeated  washings  in  fresh 
w^aters  to  remove  all  soluble  matter ;  filter  and  dry.  The  dried 
matter  is  pure  phosphate  of  lime  with  a  minute  portion  of 
partially  decomposed  carbonate. 

Take  the  powder,  calcined  and  purified  as  directed  above, 
and  make  it  into  a  paste  with  water  or  preferably  with  beer 
(Mitchell),  in  the  proportion  of  4  lbs.  of  bone-ash  to  half  a 
pound  of  beer.  The  above  mixture  is  just  sufiiciently  moist 
to  adhere  strongly  when  well  pressed,  but  not  so  moist  as  to 
adhere  to  the  finger  or  the  mould  employed  to  fashion  the 
cupels.  The  mould.  Fig.  170,  of  polished  iron,  consists  of 
two  pieces,  one  a  ring  having  a  conical  opening;  the 
other,  a  pestle  having  a  hemispherical  end  fitting  the  ^^s-  ^''^' 
larger  opening  of  the  ring.  In  order  to  mould  the 
cupels,  proceed  as  follows:  Fill  the  ring  with  the 
composition,  then  place  the  pestle  upon  it  and  force 
it  down  as  much  as  possible;  by  this  means,  the 
moistened  bone-ash  will  become  hardened,  and  take 
the  form  of  the  pestle ;  the  latter  must  then  be  forced 
as  much  as  possible,  by  repeated  blows  from  a  ham- 
mer, until  quite  home.  It  is  then  to  be  turned  lightly 
round,  so  as  to  smooth  the  inner  surface  of  the  cupel,  and 
withdrawn;  the  cupel  is  removed  from  the  mould  by  a  gentle 
pressure  on  the  narrowest  end.  When  in  this  state,  the  cupel 
must  be  dried  gently  by  a  stove;  and  lastly,  ignited  in  a 
mufl[le,  to  expel  all  moisture.     It  is  then  ready  for  use. 

There  are  two  or  three  points  to  attend  to  in  manufactur- 


222  PROCESS  OF  cupellation: — muffles. 

ing  the  best  cupels.  Firstly,  the  powdered  bone-ash  must  be 
of  a  certain  degree  of  fineness ;  secondly,  the  paste  must  be 
neither  too  soft  nor  too  dry;  and  thirdly,  the  pressure  must 
be  made  with  a  certain  degree  of  force.  A  coarse  powder, 
only  slightly  moistened  and  compressed,  furnishes  cupels 
which  are  very  porous,  and  break  on  the  least  pressure, 
and  which  allow  small  globules  of  metal  to  enter  into  their 
pores — the  most  serious  inconvenience  of  all. 

When,  on  the  contrary,  the  powder  is  very  fine,  the  paste 
very  moist  and  compressed  very  strongly,  the  cupels  have 
much  solidity,  and  are  not  very  porous,  the  fine  metal  cannot 
penetrate  them,  and  the  operation  proceeds  very  slowly; 
besides,  the  assay  is  likely  to  become  dulled  and  incapable  of 
proceeding  without  a  much  higher  degree  of  temperature  being 
employed. — {Bertliier.) 

The  Process  of  Cupellation. — In  order  to  protect  the  cupel 
from   contact  with  the  fire,   and  at  the  same  time  allow  a 
free  access  of  the  air,  it  is  when  being  heated  placed  in  a 
muffle.     The  muffle  is  a  refractory  vessel  of  baked  fire  clay. 
Fig.  171,  arched  above,  flat  bottomed, 
Fig.  171.  g^jj(j  pierced  near  its  base  with  small 

lateral  openings  for  the  passage  of  the 
heat.  Excepting  these  apertures,  and 
that  at  the  front  for  the  introduction 
of  the  cupels  and  inspection  of  the  pro- 
cess, the  muffle  is  entirely  closed.  Its  dimensions  depend  upon 
the  size  of  the  cupel  and  of  the  furnace  in  which  it  is  to  be 
heated. 

Its  position  in  the  furnace  (Fig.  98,  and  i).  Fig.  101),  must 
be  exactly  level,  and  to  protect  it  from  the  corrosive  effects 
of  volatilized  oxides,  it  may  be  payed  over  with  a  thin  paste 
of  bone  ashes.  The  muffle  being  properly  arranged  in  the 
furnace,  and  held  firmly  in  its  place  by  lute,  the  cupels  are 

then  introduced  and  the  fuel  (char- 
Fig.  172.  coal)  ignited.     The  lead  must  be 

perfectly  pure.    It  can  be  reduced, 

II  T_J      for    this    purpose,    from    refined 

litharge.    "When  the  cupels  have 
j,.^  j_2  been  exposed  for  half  an  hour,  and 

have  become  white  by  heat,  the 
lead  is  put  into  them  by  means  of 
the  tongs,  Fig.  172,  and  as  soon 


CUPELLATION  IN  TAYLOR'S  MUFFLE.  223 

as  this  becomes  thoroughly  red  and  circulating,  as  it  is  called, 
the  metal  to  be  assayed,  wrapped  in  a  small  piece  of  paper, 
is  added,  and  the  fire  kept  up  strongly  until  the  metal  enters 
the  lead  and  circulates  well,  when  the  heat  may  be  slightly 
diminished,  and  so  regulated  that  the  assay  shall  appear  con- 
vex and  ardent,  while  the  cupel  is  less  red — that  the  undula- 
tions shall  circulate  in  all  directions,  and  that  the  middle  of 
the  metal  shall  appear  smooth,  surrounded  with  a  small  circle 
of  litharge,  which  is  being  continually  absorbed  by  the  cupel. 
This  treatment  must  be  continued  until  the  metal  becomes 
bright  and  shining,  or  is  said  to  Higlden;'  after  which  cer- 
tain prismatic  colors,  or  rainbow  hues,  suddenly  flash  across 
the  globules,  and  undulate  and  cross  each  other,  and  the  latter 
metal  soon  after  appears  very  brilliant  and  clear,  and  at  length 
becomes  fixed  and  solid.  This  is  called  the  'brightening^'' 
and  shows  that  the  separation  is  ended.  In  conducting  this 
process,  all  the  materials  used  must  be  accurately  weighed, 
especially  the  weight  of  the  alloy  before  cupellation,  and  the 
resulting  button  of  pure  metal.  The  difference  gives  the 
quantity  of  alloy." 

When  the  operation  is  completed,  the  cupel  is  to  be  with- 
drawn from  the  fire  and  allowed  to  cool,  and  the  metallic 
button  then  removed  with  the  pincers.  If  the  assay  is  a  good 
one,  it  will  detach  easily.  The  button  should  be  round  and 
brilliant  upon  its  upper  surface,  but  rough  and  striated  at  the 
bottom.  If  its  surface  is  dull  and  flat,  too  much  heat  has 
been  employed;  on  the  contrary,  when  it  is  spongy,  adheres 
tenaciously  to  the  cupel,  and  contains  scales  of  litharge,  there 
has  been  a  deficiency  of  heat,  and  the  fire  must  be  again  urged 
and  the  flowing  of  the  metal  promoted,  by  adding  to  the  cupel 
a  little  powdered  charcoal.  Complete  fusion  is  indispensable 
to  the  success  of  the  operation.  If  too  much  lead  has  been 
added,  the  cupel  is  allowed  to  cool,  the  button  carefully  sepa- 
rated so  as  to  be  free  from  adherent  particles  of  ash,  and 
transferred  to  a  fresh  cupel  and  the  process  continued.  In 
experienced  hands,  the  pneumatic  blast,  p.  169,  may  be  made 
to  replace  the  furnace  in  the  process  of  cupellation. 

Cupellation  in  Taylor  s  Muffle. — Mr.  T.  Taylor  {Memoirs 
of  Chem.  Soc,  vol.  iii.  p.  316),  claims  for  his  new  form  of 
muflfle  the  following  advantages: — "1st.  Crucibles  may  be 
maintained  at  a  much  higher  temperature  than  can  be  readily 
obtained  when  the  ordinary  muflSe  is  used,  while  the  degree 


224  CUPELLATION  IN  TAYLOR'S  MUFFLE. 

of  heat  and  the  quantity  of  air  admitted  may  be  regulated 
with  the  greatest  nicety.  2d.  Owing  to  the  greater  draught 
of  air,  the  oxidation  of  the  lead  (in  the  process  of  cupellation) 
is  more  quickly  effected;  and  lastly,  by  looking  through  an 
opening  in  the  furnace  cover,  the  operation  may  be  watched 
from  first  to  last. 

''Two  black  lead  crucibles  of  the  same  size  are  ground  flat, 
so  that  when  applied  one  to  the  other  they  may  stand  steady. 
An  oblong  or  semicircular  notch  is  cut  out  of  the  mouth  of 
one  of  the  crucibles,  and  a  hole  is  also  drilled  through  its  bot- 
tom. This  crucible,  when  placed  on  the  top  of  the  other, 
constitutes  the  muffle,  and  of  course  resembles  in  shape  a 
skittle.  To  cupel  with  this  apparatus,  the  lower  crucible  is 
nearly  filled  with  clean  sand,  set  upon  the  bars  of  the  grate 
in  the  centre  of  the  furnace  and  brought  to  a  low  red  heat. 
The  cupel  containing  the  lead  of  the  alloy  is  then  placed  upon 
the  sand  and  immediately  covered  by  the  crucible,  taking  care 
that  the  notch  in  its  side  shall  be  opposite  to,  and  correspond 
with,  the  furnace  door;  more  fuel  is  added,  during  which  it  is 
well  to  cover  the  hole  in  the  top  of  the  muffle  with  a  crucible 
lid  in  order  to  prevent  the  admission  of  dirt.  When  the  muffle 
has  become  throughout  of  a  bright  red  heat  the  furnace  door 
is  thrown  open,  and  the  ignited  fuel  gently  moved  aside  so  as 
to  permit  a  view  of  the  side  opening  in  the  muffle.  The  cur- 
rent of  air  which  is  thus  established  through  the  muffle  in- 
stantly causes  rapid  oxidation  of  the  lead,  and  this  may  be 
regulated  at  pleasure  by  closing  the  door  more  or  less.  If 
from  the  fuel  falling  down,  any  difficulty  should  be  experienced 
in  maintaining  a  free  passage  for  the  air,  a  portion  of  a  por- 
celain tube,  or  a  gun-barrel,  may  be  passed  through  the  fur- 
nace door  to  within  an  inch  of  the  muffle ;  but  this  proceeding 
is  generally  rendered  quite  unnecessary,  by  taking  care  to 
place  some  large  pieces  of  coke  immediately  round  the  door 
of  the  furnace." 


SUBLIMATION  : — DISTILLATION.  225 


CHAPTER    XVII. 

SUBLIMATION. — DISTILLATION.       . 

When  simple  or  compound  bodies  which  are  either  wholly 
or  in  part  capable  of  assuming  the  aeriform  state  are  sub- 
jected to  heat,  they  or  their  most  volatile  constituents,  upon 
reaching  the  required  temperature,  rise  in  the  form  of  vapor. 
If  these  vapors,  in  their  transit,  are  intercepted  by  a  surface 
of  a  lower  temperature,  they  condense  and  take  a  solid  or 
liquid  form,  according  to  their  nature.  If  the  product  is  a 
solid,  it  is  termed  sublimate^  and  the  process  by  which  it  is 
obtained  is  sublimation; — if  it  is  liquid  or  gas,  it  takes  the 
name  of  distillate^  and  the  operation  which  yields  it  that  of 
distillation. 

Both  of  these  processes  are  indispensably  useful  in  chemis- 
try, for  they  afford  the  facility  of  taking  advantage  of  the 
unequal  volatility  of  bodies  for  their  separation. 

As  instances  of  sublimation,  w^e  have  calomel  and  corrosive 
sublimate  made  by  heating  equivalent  proportions  of  sulphate 
of  mercury  and  common  salt;  benzoic  acid  evolved  from  the 
gum ;  pure  indigo  from  the  commercial  article,  and  camphor 
from  the  crude  material.  Iodine  is  sublimed  to  free  it  from 
impurities ;  biniodide  of  mercury  to  convert  it  into  crystals  ; 
naphthalin  to  free  it  from  empyreumatic  matter,  and  succinic 
acid  to  separate  water. 

In  like  manner,  multitudes  of  instances  of  the  importance 
of  distillation  in  the  everyday-processes  of  the  chemist  and  the 
manufacturer  might  be  adduced.  It  is  employed  in  the  sepa- 
ration and  rectification  of  alcohol,  the  preparation  of  the 
ethers,  of  many  mineral  and  vegetable  acids,  and  of  a  very 
great  number  of  other  chemical  products. 

sublimation. 

The  implements  of  sublimation  are  manifold,  and  vary  in 
size  and  construction  with  the  quantity  of  the  substance  to  be 
heated,  the  nature,  degree  of  volatility  and  the  afiinity  of  the 
subliming  body  for  the  oxygen  of  the  atmosphere. 


226  SUBLIMATION  ; — IN  TUBES. 

There  are  certain  rules  to  be  observed  in  order  to  a  suc- 
cessful execution  of  the  process ;  but  whatever  the  apparatus, 
its  arrangement  and  management  must  be  such  that  there 
shall  be  no  diminution  of  the  temperature  of  the  vaporized 
matter  until  it  reaches  the  recipient  in  which  it  is  to  be  refrige- 
rated and  condensed. 

The  covers  of  flat  subliming  vessels  and  the  recipients  or 
condensing  portions  of  those  of  other  shapes,  must  invariably 
be  out  of  and  above  the  fire  and  exposed  to  the  cooling  influ- 
ence of  air.  When  the  sublimed  particles  are  very  volatile,  it 
will  even  be  necessary  to  promote  their  condensation  by 
covering  the  recipient  with  rags,  which  are  to  be  kept  con- 
stantly wet  with  cold  water  or  some  other  refrigerant. 

The  usual  mode  of  heating  subliming  vessels  is  by  the  sand 
bath,  but  for  some  substances  requiring  a  very  high  tempe- 
rature for  their  volatilization,  direct  fire  is  necessary,  and  this 
is  applied  with  the  lamp  in  small  and  nice  operations,  and  in 
larger  ones  with  the  furnace. 

In  order  to  prevent  explosion,  the  small  opening  in  the 
top,  at  the  centre  of  the  refrigerant,  must  be  only  closed  with 
a  plug  of  raw  cotton  and  should  be  freed  from  obstruction  by 
occasional  poking  with  a  wire.  When  the  escape  of  vapor 
through  this  hole  is  rapid,  the  heat  is  too  high  and  must  be 
diminished  immediately. 

After  the  completion  of  the  operation,  the  apparatus  must 
be  left  to  cool  before  it  is  opened  or  the  recipient  removed. 

The  necessary  breaking  of  close  vessels  for  the  removal  of 
the  contents,  renders  their  use  expensive ;  whenever,  therefore, 
the  nature  of  the  substance  will  permit,  an  alembic  with  de- 
tached head  should  be  preferred.  Such  vessels  are  more 
economical  and  easy  of  management,  but  generally  require 
that  their  joints  be  made  impermeable  by  luting. 

Sublimation  in  Tubes. — Sublimation  is  very  available  in 
analyses  for  detecting  the  presence  of  minute  quantities  of 
volatile  metals,  acids,  and  other  substances,  the  implement 
for  the  purpose  being  a  small  tube  of  such  forms  as  is  shown 
in  Figs.  168,  174.  After  the  introduction  of  the  substance, 
previously  powdered  and  dried,  the  tube  is  drawn  out  at  its 
open  end  to  a  fine  orifice  and  the  lower  part  heated  gradually 
over  the  flame  of  a  spirit  lamp  (Fig.  174).  The  volatilized 
portion  will  be  condensed  upon  the  sides  of  the  upper  and 
cooler  parts.     By  dividing  the  tube  with  a  file,  the  sublimate 


SUBLIMATION  IN  FLASKS. 


22T 


Fig.  174. 


Fig.  175. 


can  be  exposed  for  microscopic  examination  or  removed  for 
further  assays  under  the 
blow-pipe.  The  tubes  for 
sublimation  may  be  from  4 
to  8  inches  in  length  and 
from  an  eighth  to  half  an 
inch  in  diameter,  according 
to  the  quantity  of  the  matter 
to  be  sublimed  and  the  re- 
quired delicacy  of  the  ope- 
ration. 

Berzelius  uses  a  tube  en- 
tirely open  at  the  upper  end 

for  those  sublimations  in  which  there  are  two  volatile  products, 
of  which  one  is  to  be  drawn  off  entirely  in  the  form  of  gas  by 
the  absorption  of  oxygen  from  the  atmosphere  and  recognized 
by  its  odor,  and  the  other  condensed  in  the  upper  part  of  the 
tube,  as  for  example  a  mixture  of  sulphur  and  selenium. 

Faraday  gives  the  form  of  a  tube  apparatus  (Fig.  175)  for 
condensing  heavy  vapors  or  easily 
fusible  substances,  as  naphthaline, 
iodine,  &c.  The  bent  tube  6  is  of  a 
diameter  only  large  enough  to  allow 
its  free  passage  over  the  subliming 
tube  a.  The  upper  part  of  the  middle 
portion  of  the  tube  may  be  kept  cool 
by  paper  or  cloth  wrappers  moistened  with  water  in  order  to 
promote  the  condensation  of  the  sublimed  matter.  The  heat 
of  the  spirit  lamp  is  sufficient  for  these  small  operations,  and 
the  apparatus,  as  adjusted,  may  be  properly  maintained  by 
the  upright  clamp.  Fig.  139. 

Suhlimation  in  Flasks. — Florence  or  sweet  oil  flasks  are 
well  adapted  to  purposes  of  sublimation  on  account  of  their 
cheapness,  uniformity  of  thickness,  and  power  of  resisting 
high  heats.  Having  received  their  charge  they  are  to  be 
imbedded  in  a  sand-bath  to  a  depth  above  the  level  of  the 
contents,  and  heat  is  to  be  applied  gradually  until  the  proper 
temperature  is  arrived  at.  The  position  of  the  flask  should 
be  inclined  so  that  its  neck  may  lead  directly  into  the  reci- 
pient, as  shown  in  Fig.  176.  In  this  manner  considerable 
quantities  of  matter  may  be  operated  upon  even  at  high 
temperatures,  the  glass  bearing  a  red  heat  without  injury. 


228 


SUBLIMATION  IN  RETORTS, — CRUCIBLES. 


Another  mode  of  arranging  a  flask  for  this  process  is  to  con- 
nect its  neck  in  the  manner  of  a  hood,  with  a  long  bent  tube 
leading  into  the  refrigerant  and  recipient,  as  shown  in  Fig. 


Fig.  17G. 


Fig.  177. 


177.  The  inconvenience  of  this  arrangement  is  the  conden- 
sation of  the  gaseous  matter  in  the  tube,  the  obstruction  from 
which  may,  without  great  care,  cause  the  explosion  of  the 
flask. 

Flat  bottomed  flasks  of  thin  German  glass  are  sometimes 
used,  but  they  are  more  expensive  than 
oil  flasks.  Their  position  in  the  sand- 
bath  is  upright  and  the  flange  around 
their  necks  acts  as  a  support  for  an  in- 
verted globular  flask  which  serves  as  a 
recipient.  This  arrangement,  shown  in 
Fig.  178,  is  admirable  for  the  sublima- 
tion of  substances,  the  volatile  products 
of  which  are  so  aggregated  as  to  form 
what  are  called  flowers. 

Sublimation  in  Retorts. — Glass  retorts 
are  more  expensive  and  less  convenient 
than  flasks,  except  for  the  sublimation  of 
very  volatile  matters.  They  are  arranged 
as  shown  by  Fig.  183,  the  beak,  like  the 
neck  of  the  flask,  leading  into  a  wide- 
mouthed  receiver.  The  alembic.  Fig. 
179,  is  frequently  substituted  for  retorts 
and  is  more  convenient,  as  its  head  being 
detached  from  the  body  allows  the  more  easy  removal  of  the 
sublimed  product. 

Earthenware  retorts  with  loose  heads.  Fig.  180,  to  be 
fastened  by  pins  and  lute,  are  employed  for  sublimations  re- 
quiring high  temperatures. 

Sublimation  in  Crucibles. — The  crucible  for  this  purpose 


SUBLIMATION  IN  SHALLOW  VESSELS.  229 

may  be  of  clay,  platinum  or  iron,  according  to  the  nature  of 
the  substance  to  be  heated.  It  is  first  coated  with  a  layer  of 
refractory  clay  paste  and  when  this  is  dry,  placed  over  a 
furnace  fire.  An  inverted  crucible  of  the  same  size  with  a 
small  hole  in  its  top,  is  then  placed  over  as  a  recipient  of  the 

Fig.  179.  Fig.  180. 


vaporized  particles.  The  top  crucible  must  be  above  and  out 
of  the  fire.  When  the  operation  is  finished,  and  the  ap- 
paratus has  cooled,  the  top  may  be  removed  and  the  crucible 
emptied  of  its  contents. 

Sublimation  in  Shallow  Vessels. — In  the  treatment  of  sub- 
stances which  sublime  at  a  low  heat,  a  plate  or  capsule  resting 
upon  hot  sand  and  surmounted  by  a  glass  funnel  or  a  cone  of 
glazed  paper,  as  a  condenser  and  recipient,  answers  every 
purpose,  particularly  in  the  sublimation  of  organic  substances. 
The  top  of  the  funnel  and  cone  should  be  drawn  out  to  a 
small  opening,  and  when  the  operation  is  finished  the  contents 
of  the  refrigerant  may  be  removed  by  a  feather. 

When  iron  capsules  are  used,  as  is  often  necessary  in  sub- 
limations requiring  high  heat,  they  should  be  lined  with  a  thick 
dough  of  fire  clay.  Capsules  with  flat  bottoms  and  of  thick 
sheet  iron  are  most  appropriate.  Their  dimensions  may  be 
six  inches  in  diameter  and  J  to  1  inch  in  depth.  The  top 
B  must  be  of  earthenware  and 
detached.     The  arrangement  is  Fig.  18 1. 

shown  in  Fig.  181.  This  im- 
plement requires  a  furnace  heat. 
The  cover  should  be  tightly  ce- 
mented with  fire  lute,  and  when 

the  whole  has  cooled,  the  cover  may  be  taken  off  and  the  ad- 
herent mass  of  sublimate  removed  with  a  spatula.     The  small 


230 


HYDRO-SUBLIMATION. 


cone  c  is  to  be  kept  over  the  hole  in  the  cover  to  arrest  any 
escaping  vapors.  When  it  is  necessary  to  probe  the  cavity  it 
may  be  temporarily  removed  with  the  tongs.  A  diaphragm 
of  porous  white  paper  will  arrest  the  passage  of  any  empy- 
reumatic  matter  and  pass  the  sublimate  free  from  color. 

Two  very  concave  watch  glasses,  placed  the  one  upon  the 
other  with  their  convex  surfaces  outward,  make  a  very  neat 
subliming  apparatus  for  minute  quantities  of  rare  matter. 

Ures  Apparatus. — This  is  a  very  convenient 

Fig.  182.       arrangement.  Fig.  182,  consisting  of  two  metallic, 

glass  or  porcelain  vessels.     The  lower  one  is  the 

recipient  of  the  matter  to  be  sublimed,  and  the 

upper  a,  which  is  the  larger,  covers  the  former, 

and  is  to  be  filled  with  cold  water  to  be  replaced 

as  fast  as  it  evaporates.     When  the  process  is 

completed,  the  sublimed  matter  can  be  removed 

from  the  exterior  of  the  cover. 

Henry  8  Apparatus  for  Hydro- Sublimation. — This  arrange- 

Fig.  183. 


ment,  shown  in  Fig.  183,  has  been  proved  by  experience  to 
be  practically  useful.  It  is  employed  in  manufacturing  labo- 
ratories for  the  sublimation  of  calomel,  but  is  equally  appli- 
cable for  other  substances ;  and  by  lessening  the  dimensions 
of  the  several  pieces,  may  be  made  very  convenient  for  experi- 
mental purposes. 

It  consists  of  a  large  globular  glass  vessel  a,  with  a  long, 
straight  neck,  and  two  short,  lateral  tubulures  of  equal  width. 


HENRY  S  APPARATUS  FOR  HYDRO-SUBLIMATION. 


231 


Por  manufacturing  purposes  the  globe  must  be  of  stone-ware, 
and  of  two  or  more  gallons  capacity.  In  either  case  it  rests 
upon  the  ledge  of  a  blue  stone-ware  cylinder  A,  containing 
sufficient  water  to  close  the  neck  of  the  globe  which  dips 
lightly  into  it.  One  of  the  tubulures  receives  the  neck  of  the 
retort  6,  and  the  other  that  of  the  still,  Fig.  13,  which 
furnishes  the  steam,  or,  what  is  better,  the  conduit  pipe  of 
the  generator.  Fig.  10.  The  retort  5,  of  earthen-ware,  or 
iron,  coated  interiorly  with  fire  clay,  is  for  the  evolution  of 
the  calomel  or  sublimate  in  vapors.  It  is  wholly  enclosed  in 
the  furnace,  and  its  very  short  neck  passes  immediately  from 
it  into  the  globe  a,  so  as  to  prevent  the  condensation  of  the 
sublimate  in  the  neck  and  upper  portion.  The  joints  should 
be  tightly  luted.  The  success  of  the  operation  depends 
mainly  upon  a  proper  management  of  the  fire  and  supply  of 
aqueous  vapor.  The  heat  should  be  just  sufficient  to  drive 
over  the  sublimate  slowly,  and  the  steam  should  be  supplied 
in  large  excess,  and  simultaneously  with  the  appearance  of 
the  vaporized  solid.  For  this  purpose  the  steam  conduit  must 
be  fitted  with  a  cock  for  the  regulation  of  the  flow  of  its  con- 
tents of  vapor.  As  soon  as  the  sublimed  molecules  come  in 
contact  with  the  aqueous  vapor,  they  are  condensed  in  the 
globe  a,  and  precipitate  as  powder  (p.  84)  into  h. 

By  increasing  the  size  of  the  globe  a,  threefold,  diminish- 
ing the  orifice  of  its  neck  by  means 
of  a    small   glass   tube    traversing   a  Fig.  184. 

perforated  cork,  and  by  omitting  the 
tubulure  on  the  other  side,  the  steam 
may  be  dispensed  with  for  the  sub- 
limations of  volatile  solids  into  flowers. 
The  neck  in  this  case  must  point  up- 
wards. 

For  experimental  operations,  a  small 
earthen-ware  retort  and  glass  globe 
will  answer  every  purpose.  The  steam 
can  be  supplied  from  the  copper  wash- 
ing bottle,  Fig.  185,  by  substituting 
for  the  spirting  tube  c?,  a  flexible  leaden 
pipe  c,  which  is  to  be  connected  with 
the  neck  of  the  flask  by  a  coupling 

screw  a.  The  gas  or  spirit-lamp  will  furnish  ample  heat  for 
the  generation  of  steam  in  this  apparatus. 


232 


STEAM  SPRITZ. — DISTILLATION. 

Fig.  185.  Fig.  186. 


<^3>^^ 


DISTILLATION. 

A  process  bj  which  substances  are  heated  for  the  separa- 
tion of  a  volatile  from  a  more  fixed  portion.  The  apparatus 
for  the  purpose  consists  of  a  close  vessel  in  which  the  heating 
takes  place,  a  refrigerant  for  the  condensation  of  volatilized 
particles,  and  a  recipient  for  the  retention  of  the  product ; 
the  two  latter  purposes  being  often,  however,  fulfilled  bj  the 
same  vessel.  When  this  product  condenses  as  a  fluid,  the 
process  takes  the  name  of  liquid  distillation,  and  if  as  a  gas, 
of  gaseous  distillatio7i.  The  subjection  of  a  body  to  very  high 
heat,  for  the  purpose  of  decomposing  it  and  receiving  the 
generated  products,  is  called  dry  or  destructive  distillation. 
In  Sublimation,  which  may  be  styled  solid  distillation,  the 
volatilized  matter  is  received  and  condensed  in  one  vessel 
without  the  necessity  of  an  intermediate  refrigerant. 

The  process  of  distillation  is  one  of  the  most  indispensable 
in  chemical  investigation,  as  by  its  aid  we  can  not  only  sepa- 
rate liquids  of  diflerent  volatility,  but  also  collect  new  vola- 
tile products  which  may  result  from  the  decomposition  of  sin- 
gle or  mixed^ubstances.  As  instances  of  its  valuable  use,  we 
can  by  its  aid  separate  the  essential  oil  and  volatile  constitu- 
ents of  plclfnts  and  of  other  materials, — recover  alcohol,  ether, 
or  any  valuable  volatile  liquid,  from  solutions  in  which  they 


^' 


distillation:— THE  STILL. 


233 


are  solvents, — refine  a  liquid  from  its  fixed  impurities, — free  it 
from  fixed  matter  which  it  may  have  in  solution,  and,  aided 
by  an  absorbent  material,  remove  any  contained  water.  More- 
over it  allows  the  collection,  either  free  or  in  solution,  of  gases 
generated  by  chemical  reaction. 

The  Still. — The  still  is  the  common  implement  used  in 
large  operations  of  liquid  distillation.  It  is  generally  made 
of  copper,  and  is  tinned  internally.  A  convenient  form  has 
already  been  fully  described  at  page  44.  The  figure  below, 
Fig.  187,  exhibits  another  of  handsomer  appearance,  but  con- 
structed upon  similar  principles.    It  is  mounted  in  brickwork, 

Fig.  187. 


but  can  as  readily  and  with  as  good  results,  have  its  position 
in  the  more  economical  iron  cylinder.  Fig.  12. 

By  way  of  illustrating  the  necessary  manipulations,  we  will 
describe  the  different  steps  of  the  operation  as  commonly  per- 
formed. 

The  substance  to  be  distilled  is  placed  in  the  body  A,  the 
pewter  or  tinned  copper  head  c,  is  luted  on  and  adjusted  to 
the  pewter  worm  E,  and  the  fire  is  lighted  in  the  furnace.  To 
insure  facility  of  management,  the  several  parts  of  the  ar- 
rangement should  be  made  so  as  to  fit  accurately  to  each 
other.  As  the  heat  increases,  the  contents  of  the  body  or 
cucurbit  begin  to  boil,  and  that  portion  volatilizable  at  the 
temperature  of  the  applied  heat  mounts  in  vapor  to  the  head 
16 


234  DISTILLATION  : — THE  COOLER. 

or  capital  c,  there  partially  condenses,  runs  into  the  beak  or 
neck  D,  and  ultimately  into  the  spiral  worm  e,  where,  together 
with  any  uncondensed  vapor,  it  is  liquefied  and  cooled  by  the 
surrounding  water  previous  to  its  exit  into  the  recipient  P, 
which  may  be  an  open  pan  if  the  product  is  not  volatile,  and 
a  glass  bottle  or  carboy  if  it  is.  The  cooler  I  J  K  L,  in  which 
the  worm  is  immersed,  consists  of  a  wooden  cistern  filled  with 
water  which  requires  to  be  constantly  kept  cool ;  for  this  pur- 
pose, therefore,  there  is  a  conduit  N  M  attached,  which  re- 
ceives cold  water  from  the  hydrant  pipe  R,  and  conveys  it  in 
a  constant  stream  to  the  bottom  of  the  cistern,  so  that  it  may 
displace  the  heated  water,  which  has  become  lighter  by  expan- 
sion, through  the  lateral  outlet  at  the  top.  This  water,  already 
heated,  can  be  more  economically  used  for  making  distilled 
water  than  when  cold,  as  it  takes  less  fire  to  boil  it  when 
transferred  to  the  still.  If  the  cistern  is  kept  clean,  it  makes 
an  excellent  reservoir  for  the  supply  of  hot  water  to  the  labo- 
ratory, as  the  still  is  frequently  in  use  for  making  distilled 
water,  and  for  other  purposes. 

When  fresh  additions  of  liquid  are  to  be  made  they  can  be 
poured  through  the  tubulure  A.  This  saves  the  trouble  of 
taking  oflf  the  head  of  the  apparatus,  which  need  only  be  re- 
moved after  the  completion  of  the  operation  for  the  purpose 
of  cleaning  the  still  and  its  parts.  As  the  residuum  is  in 
many  instances  as  much  the  object  of  the  process  as  the  dis- 
tillate,  it  must,  when  such  is  the  case,  be  carefully  removed 
from  the  still,  and  transferred  to  a  suitable  vessel  for  pre- 
servation or  further  reaction. 

The  size  of  the  still  varies  with  the  amount  of  material  to 
be  operated  upon.  For  the  ordinary  purposes  of  the  labora- 
tory it  need  not  exceed  fifteen  gallons  capacity.  It  must  be 
proportioned  so  as  to  have  as  much  heating  surface  as  possi- 
ble, while,  at  the  same  time,  its  height  is  sufiicient  for  the 
foaming  and  frothing  of  its  contents  without  danger  of  their 
boiling  over  into  the  neck. 

We  have  advised  a  spiral  worm  because  that  is  the  usual 
form  of  refrigerants,  an  important  point  in  the  construction 
of  which  is  to  provide  as  much  cooling  surface,  and  conse- 
quently as  great  a  length  of  pipe  as  possible  in  a  small 
space.  Schrader's  condenser,  Fig.  188,  which  is  preferred 
by  some  manufacturers,  because  more  easily  cleaned,  consists 


DISTILLATION  IN  RETORTS. 


235 


of  a  metallic  ball,  the  upper  part  of  which  projects  above  the 
water  contained  in  the  cooler.    From 
the    lower   side    of    this   ball   three  Fig.  188. 

straight  tubes  proceed,  and  conduct 
the  vaporized  particles  downwards 
into  the  exit  tube  with  which  they 
connect.  The  exit  tube  is  closed  at 
its  upper  end  with  a  cock,  and  open 
at  the  other  for  the  escape  of  the  con- 
densed liquid. 

Whatever  the  form  of  the  refrige- 
rant, its  mode  of  action  is  the  same. 
It  is  constructed  so  as  to  facilitate  as 
much  as  possible  the  perfect  and  rapid 
condensation  of  the  enclosed  vapors. 
The  greater  the  amount  of  surface 
which  it  presents  to  the  water,  the 
more  eflfectual  its  action ;  for  the 
sooner  the  heat  absorbed  by  the  dis- 
tillate in  assuming  the  gaseous  form, 
is  abstracted  by  the  surrounding  water,  the  more  rapidly  it 
becomes  condensed  and  cooled.  The  condensation  may  be 
hastened  by  surrounding  the  recipients  with  a  frigorific  mix- 
ture, which,  if  the  vessel  be  of  glass,  must  be  at  first  applied 
gradually,  lest  its  too  sudden  cooling  causes  its  fracture. 

Distillation  in  Retorts, — Retorts  are  egg-shaped  vessels, 
answering  a  more  convenient  purpose  than  the  still  in  the 
nicer  distillatory  operations.  They  are  mostly  of  glass,  but 
for  some  processes  those  of  porcelain,  earthen  and  stone-ware, 
platinum  and  iron,  are  necessary.  Retorts  are  also  used  in 
technical  operations,  and  the  laboratory  should  be  supplied 
with  a  series  ranging  from  those  of  an  half  ounce  up  to  several 
gallons  capacity.  Glass  retorts  should  be  made  of  hard,  white 
glass,  free  from  lead.  Those  of  German  crown-glass  are 
very  thin,  but  of  uniform  thickness  and  of  sufficient  strength, 
and  moreover  withstand  both  high  temperatures  and  the  cor- 
rosive action  of  acids  and  alkalies.  The  surface  must  be  per- 
fectly smooth  and  free  from  blur  or  striae. 

Some  judgment  is  required  in  the  selection  of  retorts.  One 
properly  constructed  is  exhibited  in  Fig.  189.  It  is  seen  that 
the  neck  proceeds  laterally  from  the  summit  of  the  body, 
forming  a  wide  tube  at  its  origin  which  tapers  gradually  into 


236 


DISTILLATION  IN  RETORTS. 


a  narrow  beak.  The  arch  of  the  retort  should  be  so  fashioned 
as  to  reverberate  any  particles  of  boiling  matter  that  may 
spirt  upwards  against  it,  and  thus  prevent  their  overflow  into 
the  beak.  A  large  neck  facilitates  the  process,  because  it 
allows  more  room  for  the  accumulation  of  vaporized  matter, 
and  presents  a  proportionally  less  surface  to  the  cooling  in- 
fluence of  the  atmosphere. 

It  is  very  essential  that  the  curve  between  the  neck  and 
the  body  a.  Fig.  189,  should  be  so  formed  as  to  make  the 
straight  line  a  h  form  an  obtuse  angle,  with  the  dotted  line 
h  a.  If,  on  the  contrary,  it  is  made  as  shown  by  Fig.  190, 
which  presents  the  usual  form  of  those  sold  in  the  shops,  the 

Fig.  189. 


Fig.  190. 


Fig.  191, 


vapors,  condensing  in  the  arch  as  far  as  the  dotted  line  a  5,  fall 
back  again  into  the  body,  whilst,  in  Fig.  189,  the  dividing 
line,  from  which  the  distillate  commences  to  flow,  is  much 
nearer  to  the  body.  So  that  a  retort,  like  Fig.  189,  will  dis- 
til twice  as  rapidly  as  another  similar  to  Fig.  190,  which,  how- 
ever, when  it  has  the  form  shown  by  the  dotted  lines  c  d  a, 
becomes  equally  convenient. 

The  pear-shaped  retort.  Fig.  189,  being  deeper  in  the  body 
or  bulb,  is  better  fitted  for  distilling  volatile  substances,  and 
others  which  foam  and  swell  upon  being  heated.  The  globu- 
lar form,  Fig.  191,  presents  less  depth,  but  more  heating  sur- 


DISTILLATION  IN  RETORTS. 


23T 


face,  and  is,  therefore,  better  adapted  to  those  liquids  which 
boil  quietly  and  distil  more  slowly. 

A  great  improvement  to  the  plain  retort,  is  the  addition  of 
a  glass  stoppered  tubulure  to  the  neck,  as  at  Fig.  191.  The 
tubulure  should  have  its  position  exactly  as  shown  in  the  cut, 
so  that  the  vapors  condensing  about  it  may  flow  back.  Tubu- 
lated retorts  are  preferable,  because  they  are  more  readily 
cleansed  and  charged  than  those  of  plain  shape ;  moreover, 
they  admit  of  fresh  additions  to  their  contents  without  the 
necessity  of  disturbing  the  arrangement. 

If  the  distillation  is  to  be  urged  over  an  Argand  lamp,  the 
neck  of  the  receiver  to  be  attached  to  the  retort  may  be  long, 
and  the  connection  may  be  made  by  inserting  the  beak  of  the 
latter  in  its  mouth,  Figs.  192, 193,  194,  and  by  rendering  the 


Fig.  192. 


Fig.  193. 


Fig.  194. 


joint  air-tight  with  a  wrapper  of  India  rubber  cloth,  as  shown 
at  R  in  the  figure.  The  funnel  D  is  charged  with  water  which 
flows  in  a  thin  stream,  regulated  by  the  cock  in  the  barrel, 
upon  the  receiver  covered  with  sponge  or  bibulous  rags  and 
resting  in  a  capsule  c. 


238 


DISTILLATION  IN  RETORTS. 


If  the  retort  is  to  be  heated  in  a  furnace,  and  the  receiver 
is  globular,  the  junction  of  the  beak  and  tubulure  is  tightened 
by  means  of  a  perforated  cork  through  which  the  beak  passes, 
and  furthermore,  if  necessary,  by  a  coating  of  flaxseed  and 
whiting  lute.     The  arrangement  is  shown  in  Fig.  195.     The 


Fig.  195. 


receiver  B  resting  upon  a  straw  ring  in  a  wooden  pail,  is 
cooled  by  a  stream  of  water  from  the  hydrant  pipe  I,  which, 
as  it  becomes  warm,  flows  off  into  the  funnel  d  leading  into 
the  drain. 

In  order  to  increase  the  surface  of  the  beak,  and  conse- 
quently to  facilitate  the  liquefaction  of  the  vapors  passing 
through  it  into  the  receiver,  there  is  often  placed  between  the 
beak  of  the  retort  and  the  tubulure  of  the  receivers,  but  con- 
nected with  both,  an  adapter.  Fig.  196,  a  pointed  conical 
tube  of  white  glass,  free  from  lead,  which,  when  leading  from 


Fig.  196. 


Fi-.  197. 


(tC::: 


a  condenser  to  a  bottle,  takes  a  bent  form  as  shown  in  Fig. 
197.  Fig.  198  exhibits  a  complete  arrangement  of  a  distil- 
latory apparatus,  combining  a  tubulated  retort  with  an  s  tube, 
an  adapter,  a  recipient  placed  in  a  vessel  with  a  constant 
stream  of  cold  water  flowing  into  it,  and  a  syphon  tube  with 
a  second  receiver.  The  curved  adapter  is  needed  where  the 
receiver  rests  vertically  instead  of  horizontally. 


DISTILLATION : — RECEIVERS. 

Fig.  198. 


239 


As  it  is  requisite,  frequently,  in  distilling  volatile  liquids, 
to  have  a  larger  extent  of  cooling  surface  than  is  presented 
by  the  globular  receiver,  another  form  has  been  devised  by 
Liebig  which  is  very  convenient.  It  consists  of  a  glass  tube 
25  to  30  inches  long  and  one  inch  wide,  connected  with  the 

Fig.  199. 


beak  of  the  retort  and  running  through  a  sheet  brass  cylinder 


of  20  inches  in  lenorth  and  two  or  more  inches  diameter.    The 


I 


240 


DISTILLATION  IN  TUBES. 


metal  tube  is  closed  at  each  end  with  perforated  corks,  through 
which  the  glass  rod  passes,  and  is  held  in  a  central  position. 
A  constant  stream  of  cold  water  supplied  through  the  funnel 
tube,  passes  into  the  cylinder,  surrounds  the  glass  tube,  con- 
Fig.  200. 


Fig.  201. 


denses  the  vapor  therein  contained,  and  becoming  warm,  passes 
out  through  the  exit  pipe  to  give  place  to  cooler  water.  The 
figure  above  exhibits  one  mounted  upon  an  iron  stand  with 
joint  and  sliding  rod;  from  which,  for  small  operations,  it  may 
be  detached  and  supported  by  a  wooden  clamp. 

For  micro-chemical  distillations,  the  necessary  apparatus 
may  be  formed  of  glass  tubes  blown  into  proper  shape  over  the 
blow-pipe  table.  Fig.  200  exhibits  Clarke's  tube  retort  and 
receiver: — a  the  retort  of  an  ounce  capacity,  h  the  receiver  8 
by  three  quarter  inches,  and  c  the  dis- 
tilled liquor.  The  junction  of  the  retort 
and  receiver  (d)  should  be  hermetical. 
Plain  bulbs  a  and  tubulated  b,  Fig. 
201,  are  other  forms: — the  tube  b 
of  the  latter  serves  for  the  suction 
of  the  liquid  to  be  heated,  and  may 
afterwards  be  sealed  in  the  flame  of  a 
spirit  lamp. 

The  means  of  heating  these  small 
vessels,  are  the  small  spirit  lamps  Figs. 
118,  116,  except  when  it  is  required  to  modify  the  heat  by  a 
sand-bath,  which  requires  a  larger  lamp.  The  clamp  supports 
p.  176,  heretofore  described,  are  of  very  great  convenience  in 
the  adjustment  of  these  tube  arrangements. 

A  simpler  form  of  tube  retort  is  shown  in  Fig.  202.     It  is 
readily  made  by  closing  a  tube  at  one  end  and  bending  it  in 


DISTILLATION  : — PLATINUM  RETOKTS.  241 

a  zigzag  direction  as  represented  in  the  drawing.     The  liquid 
to  be  distilled  is  at  a  and  the  recipient  at  b.     To  render  it 

Fig.  202. 


applicable  to  the  generation  and  collection  of  gases,  the  tube 
may  be  drawn  out  at  its  open  end  and  bent  downwards  if 
necessary  to  reach  the  receiver. 

Platinum  Retorts. — The  size  of  these  vessels  varies  from 
a  quart  down  to  an  ounce,  these  capacities  being  adapted  to 
all  the  purposes  of  an  analytic  and  pharmaceutic  laboratory. 
The  usual  form  is  shown  in  Fig.  203.  The  body  a  is  nothing 
more  than  a  stout  crucible  with  a  thick  rim 
d.     The  head  5,  with  the  helm  e,  should  be  Fig.  203. 

hammered  from  one  piece  or  else  very  closely       ^^^^ 
welded  together,  and  it  should  be  ground  at     ^a^^^^^^ 
its  rim  so  as  to  fit  perfectly  to  the  mouth  of    ^Sj^S^^^^ 
the  still.  W'  I 

Platinum  stills  are  very  useful  for  destruc-     Jm^    § 
tive  distillation,  for  determining  the  amount        ^^^ 
of  matter,  if  any,  lost  by  substances  at  a 
red  heat,  for  the  distillation  of  matters  not  readily  volatilized, 
of  those  which   corrode  glass,  &c.,  and  consequently,  as  a 
substitute  for  lead  in  the  preparation  of  fluohydric  acid. 

Those  of  a  large  size  should  be  fitted  with  handles  so  as  to 
diminish  their  liability  to  defacement  by  transfer  from  place 
to  place.  When  heated  over  charcoal,  they  should  be  well 
payed  over  with  an  external  coating  of  fire  clay  paste.  Other- 
wise, the  directions  for  using  the  platinum  still,  are  the  same 
as  those  given  for  the  crucible  at  p.  197.  The  gas  or  spirit  lamp 
will  furnish  the  amount  of  heat  required  for  most  operations. 

Iron   Retorts.  —  All   iron    retorts 
should  be  of  cast   metal.      A   very  ^  Fig.  204. 

neat  form  for  small  operations  is 
shown  by  Fig.  204.  A  simpler  and 
more  economical  apparatus  is  a  mer- 
cury flask.  Fig.  205,  with  an  iron  gas 
tube  or  gun  barrel  screwed  into  the 
top,  and  reaching  nearly  to  the  bot- 
tom, and  another  tube  bent  dowa- 


Fig.  204. 

4- 


242        DISTILLATION  : — IRON  AND  PORCELAIN  RETORTS. 

wards.      This   arrangement,   well   fitted   for   distilling   dry 

Fig.  205. 


substances  which  require  a  high  heat,  may  be  modified  by 

removing  the  centre  pipe  and 
Fig.  206.  inserting  a  screw  plug,   and 

thus  be  made  well  adapted  to 
the  distillation  of  mercury. 
For  distilling  naphtha,  caout- 
chicine,  and  similar  substances, 
the  usual  form  of  a  glass  retort 
is  sometimes  preferred.  Fig. 
206  exhibits  one  fitted  with  an  iron  tube  or  conduit,  for  con- 
nection with  a  condenser  or  receiver,  which  for  mercury,  may 
be  an  iron  mortar  or  very  thick  glass  bottle  half  filled  with  water. 
Plate  iron  retorts,  sometimes  used  for  the  generation  of 
gases  by  high  heat,  are  referred  to  in  the  distillation  of  vola- 
tile substances. 

All  of  these  iron*  retorts  are  heated  in  furnaces,  that  repre- 
sented by  Fig.  206  being  placed  horizontally. 
,    When  not  in  use,  they  should  be  greased  to  prevent  oxida- 
tion, and  should  be  kept  stoppered. 

Porcelain  Retorts. — These  implements,  of  shape  similar  to 
those  of  glass,  are  only  used  for  dry  distillations ;  but  re- 
quire, that  fracture  may  be  avoided,  to  be  very  carefully 
heated.  Being  opaque,  they  have  not  the  advantage  of  glass, 
which  allows  the  inspection  of  the  contents  of  the  vessel. 

*  One  per  cent,  of  platinum,  it  is  said,  renders  iron  resistant  to  acid  and  cor- 
rosive liquids. 


GENERAL  RULES  FOR  DISTILLATION.  243 

Earthenware  and  Stone  Retorts. — The  application  of  this 
ware  to  the  purposes  of  distillation  is  very  limited.  To  render 
it  impermeable  by  gases,  the  retorts  should  be  wet  with  a 
solution  of  borax,  or  else  payed  over  with  a  coating  of  paste 
made  from  9  parts  of  clay  and  1  part  of  powdered  borax,  and 
then  heated  to  fusion  and  gradually  cooled. 

Gfeneral  Mules  for  Distillation. — In  the  distillation  of  sub- 
stances which  require  a  high  heat,  the  vessel  may  be  placed 
over  the  naked  fire.  If  it  is  a  metallic  still,  the  cylinder,  Fig. 
12,  affords  every  convenience  for  heating  by  this  method. 
Luhme's  reverberatory  furnace,  Fig.  89,  is  the  proper  heating 
implement  for  earthen  and  metallic  retorts ;  and  the  spirit  or 
gas  lamp  for  those  of  glass  and  porcelain.  When  the  nature 
of  the  process  requires  a  modification  of  the  heat,  it  can  be 
accomplished  by  means  of  intermediate  baths,  which  will 
furnish  any  temperature  required  up  to  the  boiling  point — of 
mercury. 

Glass  and  porcelain  retorts  should,  if  possible,  never  be 
heated  over  the  naked  fire,  because  of  their  great  liability  to 
fracture.  The  impossibility  of  maintaining  a  uniform  heat  is 
a  serious  objection  to  this  mode,  for  the  ebullition,  though 
rapid,  is  also  unequal.  When  the  above  vessels  are  thus  heated, 
the  same  directions  are  applicable  to  their  management  as  to 
that  of  earthen  or  metallic  retorts,  though  in  the  use  of  the 
latter  less  care  is  requisite.  The  proper  position  of  the  retort 
is  in  the  centre  of  the  furnace.  Fig.  183,  upon  a  crow-foot  or 
support.  Fig.  107,  resting  on  the  grate.  The  retort  having 
been  previously  charged,  its  beak  is  then  adapted  to  the  re- 
ceiver, and  the  joints  closed  by  lute.  A  very  small  fire  is 
then  ignited  and  increased,  after  the  retort  has  become  warm, 
till  it  reaches  to  within  a  line  or  two  of  the  level  of  the  con- 
tained liquid.  If  the  coals  project  beyond  this  point,  the  sur- 
face of  the  dry  or  upper  part  of  the  retort  acquires  a  tempera- 
ture so  much  higher  than  that  of  the  substance  which  is  being 
heated,  that  the  difference  may  cause  its  fracture  when  parti- 
cles are  projected  against  it.  A  certain  degree  of  heat  in  the 
upper  part  of  the  vessel  is,  however,  necessary,  so  that  the 
opposite  condition — the  condensation  of  vapor  in  it,  may  not 
occur ;  and  where  the  retort  is  heated  unequally,  it  is  some- 
times necessary  to  place  over  it  the  dome  of  the  furnace.  For 
the  same  reason,  also,  when  a  retort  is  heated  over  a  spirit  or 
gas  lamp,  or  by  any  other  way  in  which  the  upper  portion  is 


244  GENERAL  RULES  FOR  DISTILLATION. 

exposed,  that  part  should  be  covered  with  a  dome.     Fig.  207 
exhibits  such  a  one  of  earthenware  for  large  retorts.     A  cone 

Fig.  207.  Fig.  208. 


of  pasteboard,  Fig.  208,  will  answer  better  for  smaller  vessels. 
The  notch  in  the  front  allows  its  adaptation  to  the  neck;  but 
while  adjusted  so  as  to  effectually  protect  the  upper  part  of 
the  retort  from  contact  with  air,  it  must  be  supported  so  that 
its  weight,  when  great,  shall  not  endanger  the  safety  of  the 
retort. 

The  addition  of  the  fuel  should  be  gradual,  so  that  the  fire 
may  be  only  sufficient  to  gently  boil  the  contained  liquid.  The 
coals  should  be  first  ignited  to  expel  moisture ;  and  when  the 
operation  is  nearly  completed,  the  fire  must  be  skilfully  ma- 
naged. For  greater  safety,  the  ^^lass  retorts  should  always 
be  coated  exteriorly  with  a  paste  of  refractory  clay. 

When  the  Argand  or  gas  lamp  is  used  as  the  means  of  heat- 
ing, the  retort  need  only  be  arranged  upon  a  support,  and 
brought  over  the  flame,  which  is  to  be  applied  gradually  at 
first,  and  slowly  elevated  until  the  glass  has  become  heated 
throughout. 

Fig.  195  exhibits  a  retort  properly  located  in  a  sand-bath, 
this  being  the  mode  of  heating  retorts  for  the  distillation  of  vo- 
latile liquids,  such  as  ethers  and  the  like.  The  advantage  of 
the  sand-bath  over  the  naked  fire  for  heating  glass  retorts, 
particularly  those  of  large  size,  is  that  it  imparts  a  more  uni- 
form degree  of  heat,  and  prevents  the  possibility  of  fracture 
from  sudden  changes  of  temperature.  The  sand  should  be 
fine,  and  the  layer  upon  which  the  bottom  of  the  retort  rests 
about  an  inch  or  two  deep  according  to  the  size  of  the  retort. 
The  sand  surrounding  the  retort  should  only  reach  to  the  level 
of  the  contained  liquid,  and  should  be  removed  gradually  as 
it  evaporates. 


DISTILLATION  OF  LIQUIDS.  245 

To  prevent  condensation  in  the  top,  the  upper  portion  of 
the  retort  may  sometimes  be  advantageously  covered  with  a 
woolen  cloth. 

When  the  operation  is  performed  with  a  view  to  separate 
two  liquids  which  boil  at  different  temperatures,  the  retort 
must  be  either  set  in  a  bath  which  does  not  exceed  the  tem- 
perature at  which  the  more  volatile  liquid  escapes ;  or  else, 
when  otherwise  heated,  the  temperature  must  be  regulated  by 
a  glass  thermometer.  Fig.  84,  entering  the  retort  through  its 
tubulure,  and  adjusted  by  a  perforated  cork. 

When  the  boiling  points  of  different  liquids  are  nearly  equal, 
the  density  of  one  of  them  may  sometimes  be  increased  by  the 
addition  of  some  soluble  matter,  which,  if  both  liquids  are  to 
be  saved,  can  afterwards  be  readily  removed. 

Too  sudden  ebullition  must,  in  all  cases,  be  avoided,  and 
the  fire  should  be  gradually  increased,  whether  the  heating 
vessel  be  of  glass  or  metal.  The  only  exceptions  to  this  rule 
occur  in  the  use  of  water  or  saline  baths. 

Distillation  of  Liquids. — The  still  is  the  most  convenient 
implement  for  the  distillation  of  large  quantities  of  material. 
Retorts  are  more  applicable  to  nicer  operations. 

The  arrangement  of  a  retort  for  the  process  of  distillation 
is  very  analogous  to  that  of  a  still.  The  body  is  the  recipient 
of  the  matter  to  be  heated,  and  is  the  portion  to  which  heat 
is  applied ;  the  beak  is  the  condenser,  and  the  glass  receiver, 
the  recipient  of  the  distillate.  The  exit  nozzle  fitting  upon  the 
end  of  the  worm  and  leading  into  the  recipient,  should  never 
project  so  far  as  to  dip  into  the  distillate.  If  a  globular 
receiver  is  not  at  hand,  an  ordinary  glass  bottle  for  retort 
distillations,  or  a  carboy  for  those  in  the  still,  are  excellent 
substitutes,  as  it  is  very  easy  to  make  the  connection  by 
using  a  curved  adapter.  Fig.  197,  and  adjusting  it  to  the  mouth 
of  the  receiver,  as  in  all  other  cases,  through  a  perforated 
cork. 

Sometimes  the  receivers  themselves  are  drawn  out  at  the 
neck  into  a  tube  which  enters  a  flask,  as  at  Fig.  209,  or  else 
the  tubulure  is  fitted  with  a  perforated  cork  for  the  passage 
of  a  tube  which  answers  as  well  the  purpose  of  a  conduit. 
The  flask  which  receives  this  tube  is  also  fitted  with  a  perfo- 
rated cork  through  which  passes  another  tube,  e.  Fig.  210, 
for  the  escape  of  uncondensed  vapors. 


246  DISTILLATION  OF  LIQUIDS. 

The  refrigeration  of  the  receiver  is  readily  accomplished 
by  either  of  the  arrangements  shown  at  Figs.  194,  195. 

Fig.  209.  Fig.  210. 


The  uncondensed  gases  are  allowed  exit  through  a  small  glass 
tube  adapted  to  the  tubulure  in  the  top  of  the  receiver,  and 
leading  upwards  under  a  hood,  or  else  downwards  into  a  bottle 
of  some  fluid  which  absorbs  them,  and  thus  prevents  the  con- 
tamination of  the  atmosphere. 

It  is  of  great  importance  that  the  vessels  in  use  for  distilla- 
tion should  always  be  free  from  foreign  substances;  and  both 
the  retort,  still,  adapter,  and  worm,  immediately  after  each 
process,  should  be  cleansed  by  repeated  rinsings  with  water, 
so  that  they  may  be  clean  and  ready  for  the  next  operation. 

As  the  ebullition  of  certain  liquids  is  attended  with  foaming 
and  spirting,  it  is  necessary  to  break  the  force  of  these  sud- 
den eruptions  of  vapor,  by  some  mechanical  means.  This 
can  be  effected  often  by  the  addition  of  platinum  scraps  to 
corrosive  liquids,  and  of  fragments  of  glass  to  those  which  boil 
at  low  temperatures  and  are  without  action  upon  it.  This 
precaution  prevents  damage  to  the  vessel  and  allows  the  boil- 
ing to  proceed  tranquilly.  The  use  of  the  water  bath  obviates 
the  necessity  of  this  preventive  and  is  almost  indispensable  in 
the  distillation  of  liquids  holding  in  solution  certain  vegetable 
principles. 

In  distilling  oil  of  vitriol  in  a  glass  retort,  the  deposition 
of  sulphate  of  lead  endangers  the  safety  of  the  retort  and  the 
purity  of  the  distillate  hj  an  explosive  ebullition.     To  avoid 


DISTILLATION  OF  LIQUIDS. 


247 


Fig.  212. 


this  difficulty,  Berzelius  sets  the  re- 
tort one-third  into  the  truncated  cone  ^^^'  ^^^' 
of  sheet  iron,  Fig.  211,  strews  sand 
around  the  edge  of  the  cone,  surrounds 
it  with  brick,  and  hangs  a  flat  cone  of 
sheet  iron  about  a  half  inch  above  the 
retort.  The  retort  is  half  filled  with 
acid,  and  coals  placed  on  the  cone  in- 
side the  bricks.     Another  method  he 

pursues  is  to  precipitate  the  lead  salt  by  dilution  with  water, 
to  concentrate  the  acid  in  a  platinum  capsule,  and,  finally, 
to  distil  in  a  dome-topped  furnace,  a  quiet  distillation  being 
promoted  by  the  introduction  of  platinum  wire  into  the  re- 
tort. 

If  the  retort  is  tubulated,  there  is  no  difficulty  in  charging 
it  neatly,  because  its  contents  can  be  added 
without  danger  of  spilling  through  a  wide 
barreled  funnel;  but  when  plain,  it  is  neces- 
sary, in  order  to  prevent  the  adherence  of 
particles  to  the  sides  of  the  beak,  to  stand  it 
on  end,  as  shown  in  Fig.  212,  and  to  fill  it 
through  the  neck  by  means  of  a  straight 
funnel  tube  with  its  barrel  reaching  to  the 
bottom. 

The  matters,  if  solid,  should  always  be 
bruised  or  triturated  to  powder  and  added 
portionwise.  In  this  way  the  neck  of  the 
retort  is  kept  clean. 

The  joints  of  retorts  and  glass  distillatory 
vessels  may  be  luted  with  strips  of  muslin 
soaked  in  a  solution  of  bone  glue.  Those  of  metallic  vessels, 
with  a  dough  of  whiting  and  flaxseed  meal,  which,  when  dry, 
may  be  rendered  still  more  impermeable,  by  a  covering  of 
muslin,  prepared  as  above,  with  bone  glue.  When  one  vessel 
is  adapted  to  the  other  by  means  of  perforated  corks,  these 
latter  should  be  payed  over  with  wax  or  more  economically 
with  the  flaxseed  and  whiting  dough.  If  the  distillate  de- 
composes organic  matter,  the  use  of  corks,  flaxseed  and  simi- 
lar means,  must  be  avoided,  and  the  joints  made  tight  by  using 
apparatus,  the  connecting  parts  of  which  are  nicely  adapted 
to  each  other. 


248 


DISTILLATION  OF  LIQUIDS. 


Fig.  213. 


All  matters  which  readily  generate  very  volatile  products 
should  be  distilled  over  baths,  of  which  those  made  of  liquids 
are  to  be  preferred.  It  is  very  easy  to  arrange  the  retort  in 
a  suitable  vessel,  by  resting  it  upon  a  braided  straw  ring.  Fig. 
213,  and  steadying  its  neck  in  a  clamp  support.  The  beak 
of  the  retort  should  also  be  elongated  by  at- 
taching it  to  a  Liebig  condenser.  Fig.  199,  so 
as  to  extend  the  cooling  surface.  If  the  dis- 
tillate is  readily  condensable,  the  receiver  may 
be  kept  sufficiently  cold  by  a  bath  of  cold  water, 
as  shown  in  Figs.  194,  198 ;  otherwise  the  use 
of  FRIGORIFIC  MIXTURES  becomes  necessary.  The  mixture 
should  entirely  surround  the  recipient,  and  as  it  becomes  warm 
or  liquefies,  new  portions  must  be  added.  If  ice  or  other  solid 
is  used,  the  syphon  in  position,  as  shown  at  6,  Fig.  214,  will 
keep  the  pail  constantly  free  from  the  liquefied  excess. 

Fig.  214. 


The  proper  arrangement  of  an  apparatus  with  Liebig's  con- 
denser, is  shown  in  Fig.  215. 

In  the  distillation,  particularly  of  essences  and  oils,  the 
material,  if  it  is  ligneous,  must  be  soaked,  previous  to  its 
transfer  to  the  still,  in  which  it  should  be  made  to  rest  upon 
a  cullendered  diaphragm,  Fig.  15,  to  prevent  contact  with 
the  heated  bottom  of  the  vessel.  A  proper  vehicle  is  then 
added  and  the  operation  proceeded  with.  The  water,  or 
other  liquid,  and  volatile  matter  are  vaporized,  and  the 
two  becoming  involved  pass  over  together.  When  these 
two  products  diff^er  in  density,  as  is  commonly  the  case,  a 


DISTILLATION  OF  VOLATILE  LIQUIDS. 
Fig.  215. 


249 


very  convenient  means  of  separating  them  as  they  pass 
over,  is  afforded  by  the  Florentine 
receiver,  shown  in  Fig.  216.  A  is 
the  body  of  the  recipient,  and  D  its 
mouth  through  which  the  distillate 
enters.  The  tubulure  B  is  for  the 
reception  of  the  beak  (a  curved 
glass  tube),  c.  As  soon  as  the 
condensed  distillate  reaches  the  re- 
ceiver, the  lighter  body  rises  to  the 
top,  and  there  retains  its  position, 
and  when  the  contained  amount  of  the  two  fluids  reaches  the 
level  of  the  mouth  of  the  beak,  the  one  which  is  most  dense 
runs  off.  The  level  being  kept  thus  constant,  the  lower  stra- 
tum of  fluid  is  separated  from  the  upper  as  fast  as  any  distil- 
late comes  over,  leaving  the  lighter  liquid  to  be  emptied  from 
the  receiver  after  the  completion  of  the  process. 

If  the  heavier  product  is  the  object  of  the  distillation,  as  is 
sometimes  the  case,  then  the  form  of  the  recipient  may  be 
with  advantage  varied,  as  shown  in  Fig.  217.  The  stop-cock 
in  the  barrel,  allows  its  separation  and  discharge  from  the 
lighter  body  as  soon  as  a  sufiicient  quantity  has  subsided. 

When  volatile  oils  and  some  other  bodies  are  obtained  by 
the  above  process,  the  water  which  is  generally  employed  as 
the  vehicle,  and  which  is  separated  as  we  have  described, 
should  be  reserved,  as  being  already  more  or  less  charged 


250 


COHOBATION. — RECTIFICATION. 


Fig.  217. 


2ZZ^Z2ZZZZZA 


with  volatile  matter,  it  is  economically  used  in  redistilling  the 
same  material,  in  case  it  should  yield  its 
product  reluctantly.  This  repeated  dis- 
tillation of  the  distillate  over  the  same 
material  is  termed  Oohohation  and  is  re- 
sorted to  necessarily,  in  many  instances, 
that  the  material  may  be  entirely  ex- 
hausted of  its  volatile  matter. 

Reetification  is  the  redistillation  of  the 
distillate,  either  alone  or  with  some  absor- 
bent material  to  free  it  from  water,  acid 
or  other  impurity. 

Distillation  of  Gases. — The  term 
"distillation"  cannot  in  all  instances  be  ap- 
plied with  entire  precision  to  the  processes 
concerned  in  the  manufacture  of  gases. 
But  as  gaseous  bodies  when  intended  to 
be  retained  are  usually  prepared  by  modes 
precisely  similar  to  those  employed  in 
liquid  distillation,  it  has  been  thought  pro- 
per to  introduce  their  consideration  in  this  place. 

The  generation  and  distillation  of  gases  are  generally  made 
simultaneous  operations.  As  their  elasticity  is  such  as  to 
prevent  condensation  by  ordinary  means,  they  are  either  col- 
lected in  solution  with  water,  or  other  fluid,  or  in  their  gaseous 
state  in  gasometers.  The  arrangement  of  the  required  ap- 
paratus, though  bearing  analogy  to  that  for  ordinary  distilla- 
tions, differs  in  many  little  but  material  points. 

If  the  gas  is  readily  evolved  without  the  aid  of  heat,  as  in 
the  case  of  hydrogen,  carbonic  acid,  sulphuretted  hydrogen, 
&c.,  the  generator  may  be  a  simple  flask  A,  Fig.  218.  This 
flask  is  the  recipient  of  the  material  from  which  the  gas  is  to 
be  eliminated.  The  funnel  tube,  reaching  nearly  to  its  bot- 
tom, is  the  inlet  of  the  acid,  or  other  reagent,  by  which  the 
action  is  to  be  produced,  and  the  bent  tube  is  for  the  exit  of 
the  disengaged  gas.  An  ordinary  wide-mouth  green  glass 
bottle  will  answer  the  purpose  excellently  in  most  cases,  as 
exhibited  in  Fig.  219,  which  also  shows  an  attachment  by  a 
flexible  India  rubber  joint  of  an  angular  tube,  for  passing  the 
gas  through  liquids  when  the  influence  of  its  absorption  is  re- 
quired-^as  in  the  precipitation  of  solutions  in  analysis.  When 
the  generator  is  to  be  connected  with  a  combustion  or  desic- 


DISTILLATION  OF  GASES. 


251 


CATION  tube,  as  at  Fig.  148,  the  bent  tube  can  be  removed. 
In  this  instance,  and,  indeed,  with  better  results  in  all  cases. 


Fig.  218. 


Fig.  219. 


Fig.  220. 


T? 


the  angular  tube  should  be  blown  with  a  bulb  in  its  centre  for 
the  reception  of  a  plug  of  raw  cotton,  which  intercepts  the 
passage  of  liquid. 

The  perforations  in  the  cork  must  be  only  large  enough 
for  the  transit  of  the  tubes,  and  the  joints  must  be  perfectly 
tight.  To  render  the  cork  itself  impermeable,  sealing-wax 
should  cover  both  of  its  surfaces.  This  arrangement  of  the 
tubes  obviates  all  liability  of  explosion.  If  condensation  takes 
place  in  the  interior  of  the  generating  vessel,  the  resistance 
from  the  funnel  tube  being  more  feeble  than  that  opposed  by 
the  water  of  the  trough  or  receiving  vessel,  the  air  enters. 
So  also,  if  from  any  cause  the  passage  of  the  gas  through  the 
exit  tube  should  be  obstructed,  its  pressure  upon  the  liquid  in 
the  generator  forces  it  upwards  through  the  funnel  tube,  so 
that  it  may  escape  instead  of  being  allowed  to  accumulate 
until  explosion  takes  place. 

When  it  is  desirable  to  have  the  gas  free  from  impurity,  an 
indispensable  consideration  when  it  is  to  be  used  in  analyses, 
it  should,  previous  to  its  entrance,  be  passed  through  a  small 
quantity  of  water,  or  other  fluid,  which  will  dissolve  out  or 
chemically  attract  such  foreign  matter  as  might  have  an  in- 
jurious effect  upon  the  liquid  to  be  acted  upon.     A  suitable 


I 


252 


DISTILLATION  OF  GASES. 


Fig.  221. 


arrangement  for  such  purposes,  and  one  well  adapted  to  the 
generation  of  sulphuretted  hydrogen  gas,  is  shown  in  Fig. 
221 ;  A  is  the  bottle  containing  the  protosulphuret  of  iron, 
water,  and  sulphuric  acid,  and  provided 
with  funnel  and  disengagement  tubes  as 
usual,  the  latter  plunging  in  the  water 
of  a  smaller  bottle  B,  from  which  a 
disengagement  tube  D  nearly  as  high  as 
that  of  bottle  A  issues,  so  as  to  lead  the 
gas  disengaged,  into  a  beaker  or  other 
vessel  containing  the  liquor  to  be  ope- 
rated upon :  But  the  first  disengage- 
ment tube  c  is  in  two  pieces  united  by 
Indian  rubber,  and  the  bottles  A  B  are 
connected  together  by  a  strong  band  of 
sulphurized  Indian  rubber,  or  of  gutta- 
percha G,  so  that  the  two  bottles  may  be  lifted  at  once  as  if 
they  were  in  one,  wedges  of  cork  E  E  being  forced  between 
the  two  bottles  so  as  to  keep  the  strip  of  Indian  rubber  G  and 
the  tube  c  properly  adjusted. 

When  heat  is  required  to  cause  or  to  promote  the  elimina- 
tion of  a  gas,  the  generating  vessels  may  be  either  tubes, 
flasks,  or  retorts. 

The  facility  with  which  glass  tubes  may  be  fashioned  over 
the  blow-pipe  flame,  into  any  desired  shape,  renders  them  par- 
ticularly applicable  to  small  operations.  Fig.  222  exhibits  a 
tube-apparatus  for  the  distillation  of  hydrobromic  acid.     It 

Fig.  222. 


consists  of  a  glass  tube  A  B,  to  which  is  adapted  a  disengage- 
ment tube  conveying  the  gas  under  the  bell  c,  filled  with  mer- 
cury.   The  bromine  is  placed  at  A,  and  at  B  are  small  particles 


TUBE  APPARATUS.  253 

of  moist  phosphorus  intermixed  with  bruised  glass.  Gentle 
heat  being  applied  at  A,  the  vaporized  bromine  reacts  upon 
the  phosphorus  and  water,  producing  phosphorous  acid,  and 
disengaging  hydrobromic  acid  gas,  which  passes  over  into  the 
bell-receiver  and  displaces  the  mercury. 

A  test  tube,  Fig.  116,  fitted  with  a  bent  tube,  serves  very 
conveniently  for  generating  small  quantities  of  gas  for  ana- 
lytic or  even  experimental  purposes.  Any  other  forms  that 
may  be  needed  will  be  suggested  by  the  requirements  of  the 
process  or  the  ingenuity  of  the  operator,  and  can  readily  be 
fashioned  after  the  instructions  given  upon  Glassblowing. 

Another  very  convenient  form  of  tube  generator  is  that 
known  as  Marsh's  Arsenic  Apparatus,  Fig.  223. 
It  consists  of  an  elbowed  tube  of  Bohemian  glass,  Fig.  223. 
fitted  with  a  stop-cock  and  jet,  the  whole  to  be  sup- 
ported by  a  suitable  stand  or  pedestal.  The  length 
of  the  tube  may  be  sixteen  inches,  and  its  width 
three-fourths  of  an  inch. 

The  elbow  being  charged  with  some  pieces  of 
purified  zinc,  the  liquid  containing  the  suspected 
compound  is  acidulated  with  oil  of  vitriol  and 
poured  into  the  long  leg.  The  arsenical  combina- 
tion becomes  decomposed  by  the  nascent  hydrogen 
generated  by  the  action  of  the  sulphuric  acid  upon  the  zinc 
and  water,  and  makes  its  exit  through  the  cock  at  the  short 
arm,  as  arseniuretted  hydrogen,  which  may  be  recognized 
when  ignited  by  its  bluish  white  flame,  and  the  appearance  of 
the  deposit  upon  a  porcelain  plate  held  over  it.  The  stop- 
cock allows  the  facility  of  regulating  or  stopping  off"  the  sup- 
ply of  gas  when  required. 

Next  to  the  tubes,  a  Florence  flask  is  the  most  economical 
vessel  for  conducting  small  operations.  Fig.  224  exhibits  one 
undergoing  the  process  of  being  heated  by  a  small  spirit  lamp. 
The  tripod  upon  which  the  flask  rests,  is  surrounded  by  a  tin 
plate  screen  of  a  foot  in  height,  to  confine  the  heat  of  the  lamp. 
The  exit  tube  conveys  the  gas  into  the  beaker  glass  c,  which 
contains  the  solution  to  be  saturated.  Flasks  of  very  thin 
glass,  and  made  uniform  throughout,  are  blown  expressly  for 
this  purpose,  as  shown  in  Fig.  225.  The  exit  tube  is  bent  so 
that  it  may  be  used  with  bell  glasses  over  a  pneumatic  trough, 
as  in  Figs.  222,  243. 

Retorts  are  only  convenient  when  large  quantities  of  ma- 


254 


COLLECTION  OF  GASES. 


terial  are  to  be  operated  upon,  an(^  for  most  operations  they 
should  be  made  of  hard  glass  free  from  lead.     For  those  pro- 


Fig.  224. 


Fig.  225. 


Fig.  226. 


cesses  which  require  high  furnace  temperatures  a  metallic 
retort  is  needed.     Fig.  226  exhibits  one  of  iron.     It  is  fitted 

with  a  very  convenient  coupling 
or  gallons  screw  by  which  the 
neck  may  be  connected  with 
flexible  lead  or  other  exit  pipes. 
The  accompanying  circular  plate, 
in  two  pieces,  serves  both  as  a 
cover  to  the  furnace  and  as  a 
support  for  the  neck  of  the  re- 
tort to  retain  it  in  place.  The 
cheaper  mercury  bottle  supplies 
the  place  of  this  apparatus  ad- 
mirably in  nearly  all  instances, 
and  with  the  gun  barrel  attach- 
ment, as  shown  in  Fig.  226,  or 
other  tube,  is  particularly  useful 
in  the  manufacture  of  oxygen. 

Collection  of  Gases. — Gases  are  either  collected  in  the 
aeriform  state  or  else  in  solution.  When  generated  extempo- 
raneously, merely  as  precipitants  of  some  solution,  they  are 
passed  through  the  liquid  contained  in  a  beaker  glass,  as 
at  Fig.  224,  and  Fig.  221,  a  tightly  stretched  paper  cover 
being  in  general  all  that  is  required  to  confine  the  unab- 
sorbed  excess  in  the  vessel. 

If  a  liquid,  as  well  as  a  gaseous  product,  is  generated 


COLLECTION  OF  GASES. 


255 


simultaneously,  then  the  arrangement  of  the  apparatus  may- 
be, as  shown  in  Fig.  227.  The  use  of  this  may  be  well  illus- 
trated by  a  reference  to  the  manufacture  of  nitrous  oxide  gas. 
The  nitrate  of  ammonia,  the  material  from  which  it  is  gene- 
rated, is  placed  in  the  retort,  the  beak  of  which  is  adjusted, 
by  means  of  a  perforated  cork,  to  the  tubulure  of  a  globular 
receiver.  This  receiver  in  its  turn  is  connected  by  bent  glass 
tubes,  rendered  flexible  by  a  caoutchouc  joint,  with  a  Wolffe's 
bottle.  The  latter,  deriving  its  name  from  that  of  the  in- 
ventor, consists  of  a  bottle,  the  size  of  which  may  vary  with 
the  extent  of  the  operation,  having  in  this  instance  three 
tubulures,  each  of  which  is  fitted  with  a  perforated  cork  for  the 

Fig.  227. 


passage  of  glass  tubes.  The  first  tube  a  5,  Fig.  229,  con- 
ducts the  gas  from  the  receiver.  The  central  tube  c  c?,  acts 
as  a  safety  valve :  the  gas  cannot  escape  through  it,  but  if 
condensation  ensues  within  the  bottle,  the  external  air  rushes 
in  and  prevents  the  liquid  from  running  over  into  the  reci- 
pient or  next  bottle,  if  there  are  two  connected,  by  reason  of 
absorption.  The  third  tube  a,  is  the  exit  tube  for  conveying 
the  gas  directly  into  the  recipient. 

The  retort,  receiver,  and  Wolffe's  bottle  having  been  con- 
nected together,  and  the  joints  hermetically  closed,  heat  is 
then  gradually  applied  by  means  of  the  spirit  Argand  lamp. 
The  eliminated  gas  passes  over  into  the  receiver,  there  depo- 
sits the  aqueous  vapor  with  which  it  is  involved,  and  continues 
on  to  the  Wolffe's  bottle  containing  water,  in  its  transit  through 


256  COLLECTION  OF  GASES. 

"which  it  parts  with  the  rest  of  its  aqueous  vapor,  and  its  other 
impurities,  and  ultimately  reaches  the  exit  tube  a.  If  the  gas 
is  to  be  received  into  caoutchouc  bags.  Figs.  129,  130,  and 
pages  216, 255,  for  inhalation  or  other  purposes,  the  connection 
may  be  made  directly,  as  seen  in  the  figure,  by  means  of  a 
gallows  screw,  which  allows  an  empty  bag  to  replace  another 
which  is  charged  whenever  desired.  If  the  bags  are  intended 
as  reservoirs  for  the  preservation  of  the  gas,  their  necks  are 
fitted  with  gallows  screw  stop-cocks  and  connecting  nipples. 
Those  of  small  size,  for  the  purpose  of  inhalation,  are  fitted 
with  an  ivory  mouth-piece  m.  Fig.  227. 

If  the  gas  is  to  be  conducted  into  a  Pepy's  gasometer,  as 
at  Fig.  234,  or  under  a  bell-glass  over  a  pneumatic  trough, 
as  at  Fig.  243 ;  then  instead  of  the  stop-cock  there  must  be  a 
flexible  bent  tube  of  shape  similar  to  that  attached  to  the 
flask.  Fig.  219,  adapted  to  the  third  tubulure  of  the  bottles. 
Lead  pipe  of  small  bore  may  be  used  as  a  conduit  when  the 
generated  gas  is  not  corrosive.  The  gallows  screw  then  be- 
comes the  proper  mode  of  connection. 

To  favor  the  condensation  of  the  aqueous  impurity  of  the 
gas,  the  globular  receiver  should  be  kept  cool  during  the  dis- 
tillation. So  also  the  Wolffe's  bottle  must  be  surrounded  by 
water,  or  a  cooling  mixture,  when  the  gas  is  very  volatile, 
otherwise  the  elevation  of  temperature,  which  generally  occurs, 
may  cause  its  dissipation. 

When  two  or  more  gases  are  generated  simultaneously,  they 
may  be  separated  by  the  presence  in  the  receiver  of  an  appro- 
priate liquid,  which  is  a  solvent  of  one,  but  not  of  the  other 
of  them.  Thus  oxygen  may  be  freed  from  carbonic  acid  by 
passing  the  mixture  through  a  solution  of  caustic  potassa, 
which  absorbing  the  acid,  becomes  carbonated,  and  allows 
the  transit  of  the  purified  oxygen.  This  mode 
Fig.  228.  is  adapted  for  this  and  other  purposes  in  or- 

ganic analysis,  the  requisite  apparatus  being 
a  five  bulbed  white  glass  receiver  of  the  form 
shown  by  Fig.  228.  Its  arrangement  for  the 
purpose  is  given  in  Fig.  103,  a  being  the  com- 
bustion-tube, in  which  the  substance  to  be 
analyzed  is  introduced  after  its  mixture  with 
oxide  of  copper  or  chromate  of  lead,  from 
which  it  obtains  the  oxygen  necessary  for  its 


GENERATION  AND  ABSORPTION  OF  GASES.  257 

combustion.  The  figure  represents  the  tube  in  its  position 
during  the  analysis,  in  the  trough-shaped  furnace  of  sheet- 
iron,  in  which  it  is  heated  by  being  surrounded  with  ignited 
charcoal.  By  means  of  a  perforated  cork,  the  combustion- 
tube  is  connected  with  the  tube  in  which  the  water  pro- 
duced by  the  combustion  is  condensed.  It  is  filled  with 
chloride  of  calcium  in  order  to  absorb  all  the  vapors  from  the 
carbonic  acid,  which  passes  through  it  into  the  apparatus 
m  r  Pj  through  which  it  would  be  forced,  were  it  not  absorbed 
by  the  solution  of  caustic  potassa  contained  in  the  lower  bulbs. 
After  the  completion  of  the  combustion,  the  carbonic  acid 
which  remains  in  the  combustion-tube  is  extracted  from  it,  by 
breaking  off"  its  pointed  extremity  and  applying  suction  to  the 
other  end  of  the  potassa  apparatus  at  ^,  by  which  air  is  drawn 
through  the  whole  apparatus,  and  the  carbonic  acid  absorbed 
by  its  passage  through  the  solution  in  the  potassa  bulbs.  The 
weight  of  the  water  and  the  carbonic  acid,  is  obtained  by 
weighing  the  chloride  of  calcium  tube  and  the  potassa  appa- 
ratus before  and  after  the  combustion.  For  this  purpose  each 
may  be  conveniently  suspended  to  the  supplementary  pan, 
Fig.  62,  of  the  analytic  balance,  p.  105. 

In  the  instance  we  have  been  referring  to,  the  WolflPe's  bot- 
tle is  used  for  the  purpose  of  retaining  watery  vapor  or  other 
impurities  in  its  contained  fluid.  Its  most  common  employ- 
ment, however,  is  when  the  gas  itself  is  intended  to  be  pre- 
served in  solution  in  water  or  other  fluid.  For  this  purpose, 
the  number  of  Wolfi'e's  bottles  is  often  increased  to  three  or 
more,  which  are  connected  together  by  tubes  with  flexible 
joints.  In  this  manner,  any  gas  that  has  remained  unab- 
sorbed  by  the  liquid  in  the  first  bottle,  is  successively  exposed 
to  the  dissolving  influence  of  that  in  the  others,  until  it  be- 
comes entirely  liquefied.  The  Wolfi'e's  bottles  may,  in  many 
cases,  be  well  replaced  by  wide-mouthed  jars  or  bottles,  with 
two  or  three  perforations  in  their  corks,  and  which  may  be 
made  to  answer  all  the  purposes  of  the  more  expensive  appa- 
ratus. 

Fig.  229  represents  an  apparatus  for  the  generation  and 
absorption  of  gas ;  a  being  the  heating  vessel,  the  contents 
of  which  should  fill  only  half  its  capacity,  so  that  they 
may  not  upon  too  sudden  reaction,  run  over  into  the  recipi- 
ent :  5,  the  recipient  either  for  the  condensation  of  aqueous 


258  ABSORPTION  OF  GASES  ; — WOLFFE'S  BOTTLES. 

vapor,  or  the  abstraction  of  impurity  by  a  contained  vehi- 
cle, and  the  three  Wolffe's  bottles,  half  filled  with  water,  the 

Fig.  229. 


receptacles  of  the  eliminated  gas.  As  the  volume  of  the 
liquid  in  the  "Wolffe's  bottles  increases  proportionally  to  the 
amount  of  gas  received  and  dissolved,  they  should  not  be  more 
than  half  filled  at  the  commencement.  So  also  the  interme- 
diate receiver  should  have  but  a  very  shallow  depth  of  liquid, 
else  it  will  take  up  gas  as  well  as  the  impurities,  and  thus  cause 
a  loss.  The  water  in  the  first  bottle  is  the  first  to  become 
saturated,  and  all  the  gas  which  is  not  absorbed  passes  over 
into  the  second  and  third  bottles.  This  arrangement  is  that 
usually  adapted  for  the  distillation  of  acid,  ammoniacal  and 
other  gases,  which  are  condensed  by  solution.  When  neces- 
sary, any  other  liquid  may  be  made  to  replace  the  water  in 
the  bottles.  For  example,  aqua  ammoniae  when  it  is  desired 
to  make  a  chloride  or  carbonate  of  that  base,  and  lime  milk  for 
the  solution  of  chlorine,  &c.  &c. 

When  the  gas  is  to  be  generated  by  reaction  of  liquid  upon 
a  solid,  the  latter  must  be  put  into  the  flask  before  the  stop- 
per and  tube  are  adjusted.  The  liquid  can  then  be  added 
through  the  S  tube  as  often  as  it  is  required  to  continue  the 
disengagement.     If  the  gas  is  heavier  than  the  solvent  liquid, 


ABSORPTION  OP  GASES  ; — SAFETY  TUBES. 


259 


the  disengagement-tube  need  dip  but  slightly  beneath  its  level ; 
and  vice  versa.'*' 

^  Safety  Tubes. — When  in  the  course  of  distillation,  a  mo- 
mentary suspension  of  the  heat  or  generating  impulse  causes 
a  partial  vacuum  in  the  heating  vessel,  the  liquid  into  which 
the  disengagement  tube  dips  is  forced  by  the  presence  of  the 
atmosphere  into  its  bore,  and  ultimately  into  the  vessel  itself. 

This  entrance  of  liquid  into  the  generating  vessel  may 
result  also  from  its  sudden  cooling,  by  the  entrance  of  cold 
water  or  by  other  means. 

The  results  of  this  absorption  are  sometimes  the  fracture  of 
the  vessel,  and  more  frequently  irreparable  injury  to  its  con- 


Fig.  230. 


Fig.  231. 


Fig.  232. 


tents.  To  obviate  these  inconveniences,  we  use  a  safety  tube, 
the  usual  forms  of  which  are  shown  by  Figs.  231,  232.  The 
first,  which  is  called  an  s  tube  from  its  similarity  to  that  letter, 

*  There  are  several  points  to  be  remembered  in  the  generation  and  collection 
of  gases. 

1.  AH  gases  owe  their  existence  as  such  to  a  certain  elasticity,  by  reason  of 
which  they  press  upon  the  sides  of  the  vessels  in  which  they  are  enclosed. 

2.  The  tension  or  elastic  force  of  a  gas  is  proportional  to  its  quantity: — it 
augments  with  the  temperature  and  decreases  by  refrigeration. 

3.  The  atmosphere  weighs  upon  all  bodies,  its  pressure  being  usually  equal 
to  the  weight  of  a  column  of  water  34  feet  high,  or  of  a  column  of  mercury 
30  inches. 

4.  That  liquids  (in  equilibrium)  press  equally  in  all  directions. 

These  facts,  therefore,  render  necessary  tlie  use  of  the  safety  tubes  c  c  c,  Fig. 
229,  and  Welters,  or  the  s  lube.  Figs.  230,  231,  232. 


260  ABSORPTION  OF  GASES  ; — SAFETY  TUBES. 

is  most  used,  but  either  of  them  may  be  employed  in  the  fol- 
lowing manner.  If  the  generating  vessel  has  only  one 
aperture,  its  cork  having  been  tightly  fitted  and  rendered 
impermeable  by  coatings  of  sealing  wax  or  other  cement,  on 
its  upper  and  lower  sides,  is  then  to  be  perforated  with  two 
holes,  one  for  the  transit  of  the  s  tube,  and  the  other  for  that 
of  the  exit  tube.  The  tubes  being  tightly  adjusted  in  the 
holes  as  shown  in  Fig.  230,  and  the  cork  fitted  to  the  mouth 
of  the  generating  flask,  a  quantity  of  water  or  sometimes  of 
other  liquids,  as  mercury,  is  poured  into  the  s  tube.  When, 
during  the  process,  the  level  is  stationary  in  the  bulb  B,  and 
in  the  part  A  of  the  tube,  the  apparatus  is  hermetically  closed. 
If,  however,  a  condensation  of  vapor  takes  place  in  the  inte- 
rior of  the  flask,  the  external  pressure  of  the  atmosphere 
weighs  alike  upon  the  liquid  F  of  the  trough,  and  that  in  the 
s  tube ;  but  as  the  latter  ofi'ers  the  least  resistance,  the  air  first 
makes  its  contained  fluid  advance  towards  the  flask,  and  then 
enters  in  bubbles  into  it,  thus  preventing  the  absorption  of 
liquid  from  the  trough  or  receiver. 

If  mercury  is  used,  its  relative  density  to  water  must  be  re- 
membered, and  the  column  of  metal  in  the  curve,  should  be 
as  low  as  possible.  As  a  column  of  mercury  requires  one  of 
water  nearly  fourteen  times  its  height  for  its  support,  it  fol- 
lows that  if  the  former  is  too  high,  the  gas  passes  back  more 
rapidly  into  the  recipient  during  condensation,  from  the  dis- 
engagement tube  than  the  air  traverses  the  metallic  mass  in 
the  s  tube.  Mercury  is  used  when  the  Wolff"e's  series  com- 
prises a  number  of  bottles;  so  that  the  opposing  force  of  the 
contained  liquid  may  not  be  sufficient  to  cause  the  disengage- 
ment of  the  gas  through  the  S  instead  of  the  exit  tube. 
When  operating  with  a  mercurial  trough,  the  S  tube,  Fig.  231, 
without  a  bulb  is  used.  The  quantity  of  metal  which  it 
should  receive  must  however  be  such  that  the  pressure  of  the 
gas  will  meet  with  as  strong  a  resistance  from  it  as  the  liquid 
in  the  trough.  When  flasks  are  replaced  by  retorts,  the  latter 
should  be  tubulated,  so  that  the  safety  tube  may  be  adapted 
to  its  tubulure  by  means  of  a  perforated  cork. 

If  the  retorts  are  necessarily  plain,  as  in  certain  distilla- 
tions by  furnace  heats,  then  the  safety  tube  can  be  attached 
to  the  disengagement  tube  E  Fig.  243,  over  the  blow-pipe 
flame.     The  liquid  is  introduced  at  H  i.     This  kind  of  tube 


GASOMETERS. — PEPY'S  GASOMETERS. 


261 


known  as  "Welters  is  very  fragile,  and  requires  careful  manage- 
ment and  handling. 

Grasometers. — When  the  eliminated  gas  is  to  be  preserved 
free  from  air,  in  large  quantities  for  laboratory  purposes  or 
transportation,  it  is  received  in  gasometers. 

Pepys  G-asometer. — The  most  convenient  gas  holder  is 
that  known  as  Pepy's,  Fig.  233.  It  consists  of  a  japanned 
zinc  hollow  cylinder  16  by  12  inches,  surmounted  by  a  trough 
B  of  9  by  12  inches,  making  the  total  height  of  the  apparatus, 


Fig.  233. 


r^^ 


including  that  of  the  supports,  three  feet.  Near  the  base  of 
the  cylinder  is  a  lateral  gulley  placed  obliquely  and  cut  with 
a  thread  to  receive  a  screw  plug  which  closes  it  hermetically. 
The  tube  D,  supporting  the  centres  of  the  vessels,  and  fitted 
with  a  cock,  allows  a  communication  between  the  reservoir  and 
trough.  A  second  tube  s  c  i  at  the  side,  also  fitted  with  a 
cock,  passes  from  the  upper  cylinder  into  the  lower,  and  de- 
scends, as  shown  by  the  dotted  lines,  to  within  a  few  lines  of 
the  bottom.  The  stem  e  is  merely  a  support,  and  serves  no 
other  purposes.  The  coupling  and  stop-cock  in  the  side  near 
the  top  serve  for  connection  with  a  jet,  or  for  fitting  on  a 
bag  or  ^  bladder.  The  glass  gauge  k  graduated  into  cubic 
inches,  is  adjusted  firmly  and  hermetically  by  means  of  sockets 


262  GASES  RECEIVED  IN  GASOMETERS. 

at  the  top  and  bottom  of  the  cylinder.  To  prevent  fracture 
it  is  embedded  in  a  frame-work  of  the  same  metal  as  the  gas- 
holder. 

The  manner  of  using  the  apparatus  is  as  follows: — close 
the  mouth  g,  and  fill  the  reservoir  with  water.  For  this  pur- 
pose the  water  is  poured  into  the  trough  5,  and  allowed  to 
run  down  through  the  opened  tubes  d  and  c.  The  cock  / 
being  also  opened,  the  confined  air  escapes  as  the  water  enters, 
and  in  proportion  as  the  reservoir  a  is  filled,  the  water  rises 
in  the  tube  k  and  hence  the  latter  will  indicate  when  it  is  full. 
As  soon  as  this  occurs  and  water  runs  through  the  pipe/,  the 
cock  of  the  latter  must  be  closed,  and  the  residual  air  allowed 
to  escape  through  the  still  open  tube  d.  If,  upon  gently  shak- 
ing the  vessel,  no  more  bubbles  appear,  then  all  the  cocks  are 
to  be  closed  and  the  apparatus  mounted  over  a  tub,  of  diameter 
some  six  inches  or  more,  greater  than  that  of  the  gasometer  and 
the  gullet  ^,  is  then  opened.  As  the  highest  part  of  the  edge  of 
the  inner  aperature  of  this  gullet  is  lower  than  the  lowest  part 
of  the  edge  of  the  outer  aperature,  by  a  half  inch  or  more, 
the  water  cannot  escape  unless  the  air  simultaneously  finds 
access,  inwards,  from  above,  by  leak  holes  or  otherwise.  If, 
after  the  gush  of  a  small  portion  when  the  plug  is  first  re- 
moved, there  should  be  any  further  leakage,  it  will  be  indi- 
cated by  the  gauge  tube. 

All  being  tight,  the  beak  of  the  retort,  or  end  of  the  con- 
duit tube  of  the  generating  vessel,  is  introduced  into  the 
gullet,  as  shown  at  A,  Fig.  234.  The  eliminated  gas  entering 
the  receiver,  displaces  the  water  which  escapes  at  ^,  and  falls 
into  the  pail  beneath.  As  soon  as  the  vessel  is  full,  which  will 
be  known  by  the  examination  of  the  gauge,  or  when  a  suffi- 
cient quantity  has  been  collected,  the  disengaging  tube  or 
beak  is  withdrawn,  and  the  gullet  closed  with  the  plug. 

If  it  is  desired  to  fill  a  gas  bag  from  the  reservoir,  it  must 
be  fitted  with  an  appropriate  cock  and  nipple  for  connecting 
with  the  coupling  cock/,  and  the  pressure  of  the  water  with 
which  the  trough  h  has  been  partially  filled,  should  be  made 
to  act  upon  the  gas  by  opening  the  cock  c.  So  also,  when 
the  gas  is  to  be  transvased  into  bell-glasses,  these  latter  are 
filled  with  water  to  displace  all  air,  inverted,  and  then  brought 
directly  over  the  opened  tube  c?,  as  shown  in  Fig.  234.  As 
the  water  enters  from  the  trough  through  the   tube  c,  gas 


GASES  TRANSFERRED  FROM  GASOMETERS.       263 

escapes  into  the  jar  by  the  exit  pipe  d.     When  the  vessel  is 
filled,  communication  must  be  shut  off  by  closing  the  cocks. 

When  a  greater  pressure  is  required,  than  can  be  given 
by  the  water  contained  in  the  trough,  it  can  be  obtained  by 
means  of  a  long-barreled  funnel  o.  Fig.  236.  When  this  is 
screwed  by  its  threaded  nipple  p,  into  the  socket  «,  Fig.  234, 
and  filled  with  water,  there  is  a  pressure  of  nearly  six  feet. 

Fig.  235. 


By  abridging  the  length  of  the  barrel  to  q,  the  pressure  is 
diminished  to  a  little  less  than  four  feet.  When  two  of  these 
gasometers,  filled  the  one  with  oxygen  and  the  other  with 
hydrogen,  are  united  by  means  of  a  double  jet.  Fig.  235, 
connected  by  its  branches  a  h  with  the  cocks  /  of  the  re- 
servoir, they  form  what  is  called  the  hydro-oxygen  or  com- 
pound BLOWPIPE. 

Mercurial  G-asometer. — When  the  eliminated  gas  is  soluble 
in  water  or  altered  by  contact  with  that  liquid,  it  may  with 
propriety  be  collected  over  mercury.  For  this  purpose  Pepy 
has  contrived  the  arrangement  shown  in  Fig.  237,  which  ob- 
viates the  expense  and  inconvenience  of  filling  the  cistern 
with  mercury.  It  is  made  of  iron,  and  consists  of  a  bell 
A  A  B  B,  which  has  a  cock  o  at  its  summit,  and  which  is  im- 
mersed in  a  cylindrical  iron  cistern  M  N  o  P.  This  cistern  is 
the  reservoir  for  the  mercury,  but  in  order  that  as  little  as 
possible  may  be  used,  an  iron  core  D  E  occupies  its  centre  and 
allows  an  interval  between  it  and  the  sides  of  the  cistern  only 
sufficient  for  the  jar  and  mercury  to  make  it  tight.  A  glass 
tube  a  b  cemented  tightly  to  the  top  of  this  inner  cylinder, 
traverses  it  and  serves  as  a  conduit  of  the  gas  into  the  bell, 
which  is  maintained  in  a  vertical  position  by  a  movable  elbow 
adjusted  to  the  frame  of  the  apparatus. 

A  cock  c  is  adjusted  to  the  tube  a  6,  and  puts  it  in  commu- 
nication with  the  eprouvette  or  small  inverted  bell  F,  placed 
upon  a  dish  containing  mercury. 

In  using  this  gasometer,  the  cavity  M  N  0  P  is  filled  with 


264 


MERCURIAL  GASOMETER. 


mercury,  the  cocks  c  and  e  are  opened,  and  after  the  bell  has 
been  pressed  down  to  its  full  extent  in  the  metal,  the  cock  c 
is  closed. 


Fig.  236. 


Fig.  237. 


\ 


7 


The  disengagement  tube  is  then  introduced  under  the  mouth 
of  the  eprouvette  and  the  generation  of  the  gas  proceeded  with. 
Each  bubble  as  it  enters  the  bell  elevates  it  proportionately; 
and  when  it  has  received  a  quantity  equivalent  to  the  volume 
of  the  capacity  of  the  tube  and  of  the  eprouvette,  the  cock  c 
is  to  be  opened  again  and  the  bell  depressed.  The  greater 
part  of  the  gas  which  has  entered  and  the  air  with  which  it  is 
mixed,  is  thus  forced  to  escape.  A  repetition  of  this  manoeuvre 
two  or  three  times  will  insure  the  entire  expulsion  of  the  air ; 
when  the  portions  of  gas  given  off  can  be  collected  and  pre- 
served for  use.  When  the  bell  is  full,  the  cock  c  is  to  be 
closed  and  the  retort  J  removed. 

To  transvase  any  portion  of  the  gas  that  may  be  wanted 
for  use,  it  is  only  necessary  to  put  the  tubulure  c  in  commu- 


DEVILLE  S  GASOMETER. 


265 


nication  with  the  vessel  in  which  it  is  to  be  received,  by  open- 
ing the  cock  and  then  to  depress  the  bell  in  the  mercury. 

A  scale  graduated  upon  the  side  of  the  bell  will  allow  an 
estimation  of  the  volume  expended. 

Devilles  Gasometer. — This  apparatus,  constructed  upon 
the  same  principle  as  Harriot's  vase,  is  most  used  in  organic 
analysis. 

Fig.  238  exhibits  the  arrangement.  A  A  is  a  tubulated 
bottle  filled  with  water ;  and 


a  a  a  is  the  tube 
gaging  the  gas 
generator.  Each 
gas   displaces  an 


for  disen- 
from  the 
bubble  of 
equal   vo- 


Fig.  238. 


c=r 


lume  of  water,  which  is  con- 
ducted off  by  means  of  the 
syphon  h  b  h,  and  the  process 
should  be  continued  until  the 
expulsion  of  all  the  water, 
save  just  enough  to  fully  close 
the  orifices  of  the  tube. 

When  the  gas  is  to  be  dis- 
engaged for  use,  fill  the  fun- 
nel E  with  water  and  open  the 
cock/.  The  pressure  of  the 
water  descending  into  the 
flask  forces  the  gas  into  the 
tube  i  i. 

A  flexible  tube  h  i  can  then 
be  adapted  to  the  orifice  of 
the  vessel  into  which  the  gas  is  to  be  introduced. 

This  gasometer  is  especially  employed  for  holding  oxygen 
to  be  passed  over  oxide  of  copper  in  tubes,  after  organic  ana- 
lyses, and  to  remove  all  carbonic  acid  that  it  may  contain, 
it  is  passed  through  a  flask  containing  an  aqueous  solution  of 
caustic  potassa. 

The  small  bottle  c  contains  the  concentrated  sulphuric 
acid  and  the  tube  u,  potassa  in  one  branch  and  chloride  of 
calcium  in  the  other. 

If  the  oxygen  is  kept  in  this  holder  for  too  long  a  time,  it 
becomes  altered  and  contaminated  with  atmospheric  air. 

Pneumatic  Troughs. — In  most  manipulations  with  gases, 


266 


PNEUMATIC  TROUGHS. 


particularly  when  they  are  reqmred  for  immediate  use  or  for 
temporary  purposes,  they  are  collected  over  the  pneumatic 
trough.  As  the  bell  glasses*  into  which  they  are  to  be  re- 
ceived, must  first  be  freed  from  contained  air,  it  is  necessary 
to  immerse  them  in  an  appropriate  liquid.  Water  and  mer- 
cury are  the  two  fluids  almost  universally  employed,  the  first 
being  used  for  all  those  gases  which  are  not  soluble  in  it,  and 
for  some  which  are  only  so  in  a  slight  degree,  and  the  latter 
for  those  which  are  absorbed  by  water,  and  which  exert  no 
chemical  action  upon  the  mercury.  Hence  the  distinctive 
terms,  water  and  mercurial  trough. 

Water  Trough. — A  wooden  pail,  square  or  oval,  with  a 


*  Bell  Glasses — Gas  Jars  or  Receivers. — The  arrangement  of  an  experimental 
laboratory  is  incomplete  without  a  series  of  bell  glasses,  varying  in  size  from  a 
gill  upwards  to  one  gallon.  They  should  be  of  glass,  preferably  of  white  glass 
free  from  lead,  should  be  made  so  as  to  combine  strength  and  neatness,  and 
should  have  a  knob  at  the  summit  for  convenience  of  handling.  The  rim  of  the 
mouth  must  be  ground  perfectly  smooth  and  level,  so  that  when  resting  upon 
an  unground  glass  disk  or  an  even  bottomed  plate,  the  joint  may  be  tight.  Fig. 
239  exhibits  a  plain  jar  for  ordinary  uses ;  and  Fig.  240  a  similar  implement 


Fig.  239. 


Fig.  240. 


Fig.  241. 


Fig.  242. 


X 


tubulated  at  its  summit  and  closed  with  a  glass  stopper.  This  opening  not  only 
allows  the  facility  of  forming  connections  with  other  apparatus,  but  also  that  of 
filling  it  readily  with  liquid  merely  by  depressing  it  while  unstopped,  vertically 
in  the  water  trough.  The  air  escapes  through  the  tubulure  in  proportion  to  the 
rise  of  fluid  in  the  receiver,  which  when  full  is  to  be  stoppered  and  placed 
upon  the  shelf  to  receive  the  gas.     Sometimes  the  tubulures  are  fitted  with  stop- 


BELL  GLASSES  ; — GAS  JARS. 


26T 


little  management  can  be  converted  into  a  most  convenient 
water  trough,  Fig.  243.     It  should  be  of  capacity  sufficient 

Fig.  243. 


to  allow  the  thorough  immersion  of  bells  of  any  size  required 
for  experiment.  One  of  a  foot  in  depth,  sixteen  inches  in 
length,  and  ten  inches  in  width,  will  be  very  suitable; — a  ves- 
sel G  of  this  size  fulfilling  almost  all  the  requirements  of  an 


Fig.  244. 


cocks,  as  seen  in  Fig.  241,  which  add  to  the  convenience  of  the  jars  in  many 
operations,  and  particularly  when  it  is  desired  to  pass 
a  measured  quantity  of  gas  from  the  receiver  into  an- 
other vessel  attached  as  heretofore  described  at  p.  109. 
For  this  purpose  the  bell  must  also  be  graduated  as 
seen  in  Fig.  242, 

If  the  vessel  into  which  the  gas  is  to  be  received  is 
a  bladder  instead  of  a  glass  bell,  it  must  be  fitted  with 
a  coupling  cock,  freed  from  air  as  much  as  possible  by 
compression  with  the  hands,  then  connected  with  the 
air-pump,  Fig.  32,  and  p.  109,  or  syringe,  Fig.  244,  and 
completely  exhausted  by  suction.  The  cock  is  then 
closed,  the  bladder  detached  from  the  syringe,  and 
adapted  by  its  coupling  to  the  cock  of  the  bell.  Com- 
munication being  opened  the  gas  passes  into  the  bladder 
upon  the  depression  of  the  jar. 

By  grinding  the  surface  of  the  ledge  very  accurately, 
and  fitting  the  mouth  of  the  bell  with  a  ground  glass 
disc,  which  by  the  intervention  of  a  little  grease  may 
form  an  airtight  joint,  gases  may  be  retained  unaltered  for  a  limited  period. 


268  GASES  RECEIVED  OVER  WATER  TROUGHS. 

experimental  laboratory.  Near  to  the  top,  in  the  interior, 
should  be  lateral  flanges  for  the  support  of  a  sliding  shelf  a. 
This  sliding  shelf  should  have  sufficient  surface  for  the  sup- 
port of  several  bells  or  jars  F  at  a  time,  and  may  extend 
over  half  of  the  trough.  It  is  perforated  with  holes  for  the 
reception  of  the  beak  of  the  disengaging  vessel  as  seen  at  5, 
Eig.  243. 

A  very  convenient  water  bath  for  the  collection  of  gases, 
may  be  formed  of  a  deep  earthenware  dish,  or  other  vessel  in 
common  use,  by  the  addition  of  the  bee-hive  shelf.  Fig.  245. 
This  shelf,  generally  made  of  porcelain,  is  a  sub- 
Fig.  245.  stitute  for  the  shelf  of  a  regular  trough,  and  serves 
for  the  support  of  the  bell  glasses  or  other  re- 
ceivers. It  may  be  two  inches  in  diameter  and  one 
inch  high,  for  a  dish  one  foot  wide  and  two  inches 
deep,  and  proportionally  larger  for  one  of  greater 
dimensions.  The  disengagement  tube  enters  the  semicircular 
opening  at  the  base  and  delivers  the  gas  into  the  receiver  by 
its  curved  end  protruding  through  the  hole  in  the  centre. 
Part  of  a  loaded  wooden  box,  a  metallic  support,  or  other  ex- 
temporaneous arrangement  may  in  many  cases  be  so  ad- 
justed to  take  the  place  of  the  common,  or  the  bee-hive  shelf 
— and  to  answer  every  useful  purpose. 

It  is  indispensable  that  the  trough  should  be  made  tho- 
roughly water  tight  and  should  be  well  hooped.  For  further 
protection  it  might  be  covered  over  with  several  coats  of 
plumbago  paint.  Leakage  being  thus  provided  against  the 
vessel  may  be  used  upon  either  the  operating  or  centre  table. 
The  stop  cock  near  the  bottom  allows  the  exit  of  the  water 
when  it  has  become  dirty,  acidified,  or  otherwise  unfit  for 
use. 

The  level  of  the  contained  water  must  always  be  half  an 
inch  or  more  above  the  top  of  the  shelf.  When  the  bell  is  to 
be  charged,  it  is  first  completely  immersed  in  the  water  so  as 
to  expel  all  contained  air,  then  taken  up  by  the  knob,  raised 
to  a  vertical  position  and  carefully  slid  along  with  its  mouth 
in  the  water  to  the  shelf  and  placed  immediately  over  the  hole 
through  which  the  disengagement-tube  enters.  As  the  gas 
bubbles  up  into  the  bell  the  water  is  displaced,  and  when  it  is 
filled,  it  can,  if  necessary,  be  drawn  aside  and  replaced  by  an- 
other. So  the  process  is  continued  until  all  the  gas  generated 
has  been  received. 


THE  MERCURY  TROUGH. 


269 


Fig.  246. 


As  the  first  bubbles  of  gas  eliminated  are  contaminated  with 
air,  they  should  be  rejected;  consequently  the  beak  of  the  dis- 
engagement tube  ought  not  to  be  brought  under  the  bell  re- 
ceiver until  the  gas  commences  to  pass  over  freely. 

The  Mercury  Trough. — The  high  price  of  mercury  renders 
necessary  an  economical  construction 
of  the  trough  in  which  it  is  kept.  Fig. 
246  exhibits  one  of  convenient  form. 
It  consists  of  a  well-japanned  cast- 
iron  trough,  twelve  inches  long,  seven 
inches  wide,  and  two  inches  deep. 
The  bottom,  towards  the  side,  is  sunk 
throughout  its  length  into  a  well  two 
inches  wide  and  one  and  three-quarter 
inches  deep,  and  is  expanded  at  its  end 
into  a  circular  cavity.  This  cavity 
allows  of  the  immersion  of  the  tubes 
or  bells  in  a  moderate  depth  of  mercury  without  the  expense 
of  filling  the  whole  trough  being  incurred ;  and  the  circular 
end  being  larger  than  the  other  portion  of  the  canal,  allows 
the  use  of  receivers  of  from  two  to  three  inches  in  diameter. 

When  this  cavity  is  not  in  use  and  the  mercury  required  to 
fill  it  is  needed  in  the  other  part  of  the  trough,  it  is  closed 
with  an  exactly  fitting  iron  plug  which  accompanies  the  vessel 
for  this  purpose. 

The  trough  is  placed  upon  the  operating  table  and  is  mani- 
pulated with  in  the  same  manner  as  the  water  trough.  For 
the  convenience  of  supporting  tubes  in  a  vertical  position, 
there  is  generally  an  accompanying  clamp  with  sliding  rod, 
which  is  attached  to  the  side. 

The  small  mercurial  trough  of  porcelain.  Fig.  247,  very 
useful  in  organic  analysis,  contains  usually  from  ten  to  twelve 
pounds  and  serves  also  very  conveniently  for  experiments 
upon  a  small  scale. 

Fig.  248  exhibits  a  cylindrical  glass  trough  which  is  used 
."with  tubes  in  organic  analysis.  It  is  of  glass,  fifteen  and  a 
lalf  inches  high,  and  is  widened  at  the  top.  The  drawing 
•epresents  the  introduction  of  ley  into  a  graduated  tube  by 
leans  of  the  pipette  a  over  a  column  of  mercury.  The  tip 
»f  the  pipette  is  curved  so  as  to  facilitate  its  entrance  under 
bhe  mouth  of  the  tube.  This  plan  is  adopted  sometimes  in 
ieu  of  that  given  at  p.  256,  for  the  separation  of  two  gases. 


270 


GASES  COLLECTED  OVER  AIR. 


by  presenting  to  both  a  third  substance  for  which  either  of 
them  has  an  affinity. 


Fig.  247. 


Fig.  248. 


Fig.  249. 


In  the  course  of  time  the  mercury  of  the  trough  becomes 
debased,  by  use,  either  with  water,  metals,  or  suspended  mat- 
ters. The  water  being  specifically  lighter,  may  very  readily 
be  removed  by  spreading  sheets  of  bibulous  paper  on  the  sur- 
face of  the  mercury  and  renewing  them  as  fast  as  they  become 
imbued.  The  metals  are  separable  by  distillation,  the  mer- 
cury passing  over  pure  into  the  recipient. 

If  the  impurities  are  merely  coarse  suspended  particles  as  of 
metallic  oxides,  straining,  by  compression  with  the  hands 
through  a  chamois  leather  bag,  will  retain  them,  and  even 
most  amalgams,  while  the  mercury  passes  through  the  pores 
entirely  or  almost  pure. 

Gases  collected  over  air. — Although  chlorine  can  for  tem- 
porary purposes  be  collected  over  hot  water  in  which  it  is  not 
dissolved,  that  body  as  well  as  iodhydric  and  bromhydric  acids 
and  certain  other  gases  which  are  soluble  in  water,  or  which 
attack  mercury,  are  sometimes  collected  in  receivers  or  bot- 
tles filled  with  air. 

If  the  gas  is  lighter  than  air,  the  end  of  the  disengagement 
tube  should  reach  to  the  upper  part  of  the  inverted  vessel. 
As  the  gas  enters,  the  air  is  displaced  and  goes  out  below, 
and  the  jar  is  known  to  be  full  when  the  gas  escapes  also. 
The  jar  must  then  be  slowly  and  carefully  removed  so  that 
the  vacuum  left  by  the  withdrawal  of  the  tube,  may  be  com- 


TRANSFER  OP  GASES.  271 

pletely  supplied  by  the  gas  simultaneously  entering,  and  its 
mouth  be  closed  with  a  plate  of  ground  glass,  cork,  piece  of 
caoutchouc,  or  other  suitable  means. 

When  the  gas  is  heavier  than  air,  as  is  the  case  with  chlo- 
rine, the  disengagement  tube  should  enter  to  the  bottom  of 
the  receiver,  the  mouth  of  which  should  be  closely  covered 
with  a  pasteboard  disk.  When  the  gas  begins  to  escape  at 
the  mouth,  the  jar  is  full,  and,  after  being  closed  with  a 
ground  glass  plate  or  other  stopper,  carefully  removed  aside. 

Transfer  of  Crases. — It  is  frequently  necessary  to  transfer 
portions  of  gas  from  a  large  vessel  to  a  smaller  one  for  the 
purposes  of  experiment  or  measurement.*  Having  already 
given  the  mode  of  transferring  from  a  gasometer  we  will  now 
speak  of  transvasement  over  troughs. 

If  the  jar  or  reservoir  of  gas  is  still  upon  the  shelf  of  the 
pneumatic  trough,  the  smaller  vessel  which  is  to  receive  a  por- 
tion of  its  contents  is  to  be  entirely  immersed  in  the  fluid  of 
the  trough,  and  whilst  full,  conveyed  bottom  downwards  to  the 
shelf  and  there  placed,  so  that  it  will  project  over  the  edge 
about  a  third  of  its  diameter.  The  reservoir  is  then  brought 
forward  and  the  mouths  of  the  two  put  in  connection  as  shown 
in  Fig.  250  by  inclining  the  reservoir  so  that  their  edges  may 
be  in  contact; — the  gas  then  passes  up  in  bubbles  and  by  a 
little  dexterity  the  rapidity  of  its  flow  can  be  easily  regulated. 

At  pages  109,  133  and  134,  we  have  already  given  direc- 
tions for  the  transfer  of  gases  into  tubes  and  globular  vessels. 

Bladders  are  filled  from  the  cocked  receivers,  Fig.  241,  as 
directed  at  p.  267.  Bladders  are  cleansed  by  ablution  in 
weak  potash  lye,  subsequent  washings  in  fresh  water  and 
drying.  The  caoutchouc  bags,  mentioned  at  p.  216,  are 
however  preferable. 

*  As  the  volume  of  a  gas  confined  in  tubes,  or  other  vessels,  over  mercury  or 
water  varies  according  to  the  pressure  of  the  surrounding  atmosphere,  it  becomes 
necessary  in  experiments  on  gases  to  observe  the  baroinetric  pressure,  or  the 
height  of  the  mercurial  column  in  the  barometer,  at  the  time  the  volume  of  the 
gas  is  observed.  Every  laboratory  ought,  therefore,  to  be  provided  with  a  baro- 
meter, which  should  either  be  a  good  syphon-barometer  or  a  cistern-barometer, 
in  which  the  mercury  of  the  cistern  may  be  brought  to  the  same  level  before 
observing  the  height  of  the  column.  The  latter  is  generally  read  off  in  a  scale 
divided  into  inches,  tenths,  and  hundredths  of  inches.  As  the  height  of  the' 
mercurial  column  varies  according  to  the  temperature,  a  correction  must  be 
made  for  the  temperature  of  the  mercury  in  the  barometer,  which,  for  this  pur- 
pose, is  furnished  with  a  thermometer  to  be  observed  at  the  same  time. 


272 


CORRECTION  FOR  PRESSURE  AND  TEMPERATURE. 


When  the  filled  receiver  is  to  be  removed  from  the  trough 
for  further  essays  with  the  gas,  it  should  be  gently  slid  off 

Fig.  250. 


the  shelf  into  a  flat-bottomed  plate  containing  just  enough 
water  or  mercury  to  seal  the  mouth. 

Correction  for  Pressure. — The  pressure  of  the  atmosphere 
at  the  level  of  the  sea  is  equivalent  to  15  pounds  upon  each 
square  inch  of  the  earth's  surface,  and  is  capable  of  support- 
ing a  column  of  water  32  feet  high,  and  one  of  mercury  30 
inches.  The  standard  pressure,  therefore,  by  which^  the  va- 
riations at  different  levels,  and  indeed  at  the  same  level,  from 
some  unknown  causes,  are  estimated,  is  thirty  inches. 

"The  following  is  the  rule  for  calculating  the  volume  which 
a  gas  should  possess  at  one  pressure  from  its  known  volume 
at  another  pressure.  As  the  pressure  to  which  the  gas  is  to 
be  reduced  is  to  the  observed  pressure,  or  height  of  the  baro- 
meter, so  is  the  observed  volume  to  the  volume  required.  Thus, 
suppose  a  volume  of  gas  has  been  observed  at  120  cubic 
inches,  when  the  barometer  is  standing  at  28.8  inches,  we 
find  its  real  volume  at  the  normal  pressure,  thus : 

"As  30  :  28.8  : :  120  :  115.2  =  the  volume  which  the  gas 
would  occupy  at  30  inches  barometer ;  or,  if  the  barometer 
at  the  time  of  the  experiment  stands  at  30.6  then 

"As  30  :  30.6  :  :  120  :  122.4  =  the  volume  which  the  gas 
would  occupy  at  30  inches  barometer.  When  the  correction 
of  a  gas  is  to  be  made  both  for  temperature  and  pressure,  the 
reduction  is  first  made  for  temperature,  and  the  corrected 
volume  is  afterwards  reduced  according  to  the  pressure." 


DISTILLATION  IN  VACUO.  273 

a  Corrections  for  Temperature. — According  to  the  recent 
experiments  of  Regnault,  it  appears  that  a  volume  of  gas 
expands  by  heat  4igth  of  its  bulk  for  each  degree  of  Fahr., 
and  calling  the  volume  of  a  gas  at  0°  Fahr.  unity,  its  volume 
at  any  higher  temperature  is  found  by  the  formula  1   + 

— ^^r — '-    The  determination  of  the  volume  of  a  gas  at 
459 

one  temperature  from  its  known  volume  at  another  tempera- 
ture may  be  attained  by  the  following  formula : — 

"  Let  t  be  the  temperature  Fahr.  at  which  the  volume  of  gas 
is  observed,  t'  the  temperature  to  which  it  is  to  be  reduced,  x 
the  observed  volume  at  t^  and  x'  the  volume  at  t'  required. 

Then  X'  -  (M^jL05 
inen  x  -      459  ^  ^    . 

^'Example. — Suppose  the  balloon  to  be  filled  with  a  gas  at 
the  temperature  of  50°,  and  that  it  has  been  previously  as- 
certained that  its  content  is  exactly  50  cubic  inches.  The 
above  formula  enables  us  to  calculate  the  real  volume  of  the 
gas  at  the  normal  temperature,  thus: 

(459  4-  60)  X  50 

459  +  50        -  ^^'^^^' 

so  that  we  actually  have  in  the  globe  50.982  cubic  inches  of 
gas,  and  our  calculation  for  specific  gravity  must  be  made 
accordingly. 

''  Suppose,  however,  that  the  temperature  of  the  gas  is  70°, 
or  10°  above  the  normal  temperature,  we  have  then  less  than 
500  cubic  inches  present,  for 

(459  -f  60)  X  50 

459  4-70       -  ^^-^^^^ 

and  our  calculation  must  be  made  accordingly." 

Distillation  in  vacuo. — This  kind  of  distillation  is  resorted 
to  for  the  production  or  purification  of  many  volatile  matters 
which  are  alterable  in  the  air  or  in  aqueous  vapor.  Retorts 
drawn  out  at  their  beak  into  a  very  narrow  opening,  or  glass 
tubes,  fashioned  over  the  blow-pipe  flame  to  suit  the  process, 
are  the  vessels  commonly  employed.  After  the  vessel  is 
charged,  heat  is  applied  to  the  bulb  portion,  and  as  soon  as  it 
becomes  filled  with  vapor  and  all  air  is  expelled,  the  tube 
should  be  heated  over  a  lamp.     After  the  annealing  of  the 


274  DRY  DISTILLATION. — LUTES. 

closed  end,  it,  being  intended  for  the  reception  of  the  distillate, 
should  be  exposed  to  the  influence  of  cold  while  the  process 
is  being  conducted.  If  the  retort  is  used,  the  receiver  with 
which  it  is  connected  must  be  warmed  over  the  sand  bath, 
and  in  delicate  experiments  exhausted  bj  means  of  the  syringe, 
Fig.  244,  or  air-pump.  Fig.  32. 

Dry  Distillation. — The  distillation  of  a  solid  alone  and 
without  contact  with  liquid  of  any  kind  is  called  dry  or  de- 
structive distillation.  The  process  is  resorted  to  for  the  decom- 
position of  certain  bodies  more  particularly  organic,  and  their 
resolution  into  new  compounds  by  an  interchange  of  elements. 
The  products  are  generally  liquid  and  gaseous,  consequently 
the  arrangement  of  the  apparatus  must  be  with  a  view  to  the 
preservation  of  both,  the  means  for  which  have  been  already 
mentioned.  Dry  distillation  requires  a  high  heat  and  conse- 
quently very  refractory  vessels  which  must  be  kept  closed. 
As  examples,  citric  acid,  by  this  process  may  be  converted 
into  carbonic  acid  and  oxide,  acetone,  aconitic  acid,  and 
water ;  fatty  bodies  modified  into  new  substances  and  resins 
transformed  into  oily  liquids  and  gaseous  carbohydrogens. 

In  the  dry  distillation  of  nitrogenized  bodies,  the  resultant 
products  are  complex,  and  contain  nitrogen,  ammonia,  cyano- 
gen, &c.  For  instance,  indigo  yields  carbonate  and  prussiate 
of  ammonia  and  kyanole. 

In  the  arts,  the  dry  distillation  of  wood  furnishes  charcoal, 
pyroligneous  acid  and  pyroxylic  spirit  and  creasote  and  tar; 
and  that  of  bituminous  coal  and  fat,  illuminating  gas. 


CHAPTER  XVIII. 

LUTES. 

In  all  combinations  of  two  or  more  pieces  of  apparatus  or 
parts  of  them,  there  is  a  necessity,  in  chemical  operations 
generally,  of  some  means  of  hermetically  closing  the  inter- 
stices of  their  joints  so  as  to  protect  the  enclosure  from  all 
outward  communication.  This  is  particularly  requisite  in 
SUBLIMATION,  DISTILLATION  and  Other  heating  operations,  and 


LUTES  : — CAOUTCHOUC,  BLADDER,  FLAXSEED.     275 

indeed  in  all  experiments  with  gases  and  liquids,  wherever 
it  is  desired  to  confine  the  volatilized  particles  within  the 
vessels  and  prevent  their  escape  into  the  atmosphere  and  con- 
sequent loss. 

To  accomplish  these  ends  we  make  use  of  lutes,  which  must 
vary  in  composition  and  mode  of  application  with  the  material 
and  construction  of  the  apparatus,  the  temperature  at  which 
it  is  to  be  heated,  and  the  nature  of  the  generated  products. 

Caoutchouc. — This  substance,  in  sheets,  is  particularly  use- 
ful for  forming  flexible  tubes  by  which  joints  may  not  only  be 
rendered  hermetical  but  also  flexible.  For  delicate  apparatus 
it  is  particularly  applicable  even  at  high  temperatures.  The 
tubes  are  made  as  directed  at  p.  216,  and  tied  above  and 
below  the  joint  as  at  x,  Fig.  166.  Sometimes  India  rubber  is 
replaced  by  muslin,  payed  over  after  its  adjustment  around 
the  joints,  with  a  paste  made  by  the  mixture  of  caoutchouc 
and  spirits  of  turpentine. 

Bladder. — Bladder  well  cleansed  and  divided  into  strips 
answers  very  well  to  a  limited  extent.  For  example,  when 
moistened  and  coated  with  white  of  egg  or  solution  of  bone 
glue  or  of  isinglass,  it  forms  an  excellent  covering  for  the 
joints  of  retorts,  tubes  and  the  like,  to  the  surfaces  of  which 
it  adheres  tenaciously.  When,  however,  the  contained  in- 
gredients generate  corrosive  vapors,  and  so  rapidly  as  to  strain 
the  apparatus,  the  bladder  is  unserviceable. 

Flaxseed  Lute. — Flaxseed  meal  mixed  to  the  consistence 
of  a  paste  with  water,  milk,  lime-water,  or  starch  paste.  This 
lute  is  very  manageable  and  impermeable,  but  does  not  with- 
stand a  heat  greater  than  about  500°. 

If  just  the  sufficient  quantity  of  water  be  added  to  quick- 
lime to  reduce  it  to  a  dry  powder,  and  that  is  mixed  well  and 
rapidly  with  white  of  egg  diluted  with  its  own  volume  of 
water,  and  the  mixture  spread  immediately  upon  strips  of  linen 
and  applied  to  the  part,  which  is  then  sprinkled  with  quick- 
lime, a  good  cement  is  made.  Instead  of  white  of  Qgg^  lime  and 
cheese  may  be  used,  or  lime  with  weak  glue  water  or  blood. 
This  lute  dries  very  rapidly,  becoming  very  hard,  and  adher- 
ing strongly  to  the  glass ;  but  its  great  inconvenience  is  the 
want  of  flexibility. 

In  spirituous  distillations,  the  joints  of  the  apparatus  may 
be  closed  very  readily  and  eff'ectually  by  a  stifi"  paste  of  equal 
weights  of  whiting  and  flaxseed  meal,  mixed  with  water.     Wo 


276  lutes: — lime,  plastic,  kesinous. 

have  found  this  lute  invaluahle  notwithstanding  its  want  of 
flexibility.  It  is  the  most  easily  made  and /most  cleanly  of  all 
lutes,  and  when  the  pressure  of  the  contained  vapor  is  con- 
siderable, it  can  be  covered  with  strips  of  bladder  soaked  in 
solution  of  bone  glue. 

Lime  and  Bone  Glue. — Freshly  slacked  lime  made  into  a 
thick  paste  with  a  strong  solution  of  bone  glue,  makes  an 
adhesive  lute  very  applicable  for  closing  the  joints  of  vessels 
which  are  to  be  subjected  to  high  heats,  as,  for  example,  those 
in  which  the  distillation  of  lime  and  sal  ammoniac  for  the 
production  of  gaseous  ammonia  is  conducted. 

Plaster  of  Paris. — Calcined  gypsum  made  into  a  paste 
with  glue  or  starch  water,  answers  the  same  purposes  as  the 
above.  When  covered  with  strips  of  bladder  it  is  rendered 
entirely  impermeable  by  gases.  A  coating  of  oil  or  of  a 
mixture  of  oil  and  wax  has  the  same  effect  as  the  bladder, 
and  the  lute  will  then  stand  a  dull  red  heat. 

Plastic  lute,  is  made  by  dissolving  melted  caoutchouc  in 
hot  linseed  oil,  adding  finely  powdered  pipe  clay  and  knead- 
ing the  whole  together  into  a  homogeneous  mass.  The  longer 
it  is  kneaded  the  better  is  its  quality,  and  to  prevent  its  hard- 
ening the  caoutchouc  should  not  be  in  deficient  proportion. 
If  it  should  become  hard  by  keeping,  it  may  be  softened  by 
kneading  with  a  little  spirits  of  turpentine. 

This  lute  closes  the  joints  without  hardening,  and  can  be 
removed  at  any  time  during  the  operation,  to  allow  a  change 
in  the  position  of  the  parts  of  the  apparatus. 

For  the  distillation  of  acids  or  other  corrosive  vapors,  it  is 
very  applicable. 

Soft  cement  is  prepared  by  fusing  yellow  wax  with  half  its 
weight  of  crude  turpentine  and  a  little  Venetian  red,  in  order 
to  color  it.  It  is  very  flexible,  and  takes  any  desired  form 
under  the  pressure  of  the  fingers.  It  is  extremely  useful  at 
common  temperatures  for  tightening  tubes  in  cork,  and  as  a 
coating  for  rendering  corks  impermeable  to  gases. 

Resinous^  or  hard  cement,  is  made  by  fusing  together  at 
the  lowest  possible  temperature,  1  part  of  yellow  wax  and  5 
or  6  of  resin,  and  then  adding  gradually,  1  part  of  red  ochre, 
or  finely  powdered  brickdust,  (plaster  of  Paris  succeeds  very 
well,)  and  then  raising  the  temperature  to  212°  at  least,  until 
no  more  froth  arises,  or  agitation  takes  place,  and  stirring  it 
continually  until  cold.     This  cement  is  employed  in  a  hot 


LUTES  : — GLASS,  IROX,  FIRE.  277 

state,  and  is  very  much  used  for  fixing  brass  caps,  &c.,  to 
air  jars,  and  as  an  impermeable  coating  for  the  interior  of 
wooden  vessels. 

Lute  for  joining  Glass  and  Steel. — A  saturated  solution 
of  mastic  in  alcohol,  mixed  with  a  solution  of  isinglass  in 
dilute  spirits,  to  which  is  added  a  small  portion  of  galbanum 
or  ammoniac,  is  an  excellent  cement  for  joining  glass  to  glass 
or  glass  to  steel.  The  mixture  must  be  kept  in  a  well-stopped 
bottle,  and  be  always  warmed  previous  to  use. 

Hover  (Phila.)  makes  an  excellent  cement,  which  answers 
the  purposes  of  the  above,  and  is  very  useful  in  the  labora- 
tory for  mending  broken  vessels  for  dry  operations. 
L      Lute  for  joining  Orueihles. — A  mixture  of  fine  clay  and 
i ground  bricks  kneaded  into  a  paste  with  water,  holding  in 
"  solution  one-tenth  of  borax,  answers  admirably  for  luting  the 
joints  of  superposed  crucibles.     An  excellent  lute  for  this 
purpose  and  also  for  metallic  subliming  vessels,  is  finely  pow- 
dered Stourbridge  clay,  containing  a  little  sal  enixum,  and 
made  into  a  stifi"  paste  with  water. 

Iron  Cement. — This  mixture  is  used  for  making  permanent 
joints  generally  between  surfaces  of  iron.  Clean  iron  borings 
or  turnings  are  to  be  slightly  pounded  so  as  to  be  broken  but 
not  pulverized ;  the  result  is  to  be  sifted  coarsely,  mixed  with 
powdered  sal-ammoniac  and  sulphur,  and  enough  water  to 
moisten  the  whole  slightly.  The  proportions  are,  1  sulphur, 
2  sal  ammoniac,  and  80  iron.  No  more  should  be  mixed 
than  can  be  used  at  one  time. 

Fire  Lute. — The  best  fire  lute  is  that  employed  by  Mr. 
Parker,  and  is  composed  of  good  clay  2  parts,  sharp  washed 
sand  8  parts,  horse-dung  1  part.  These  materials  are  to  be 
intimately  mixed;  and  afterwards,  the  whole  is  to  be  tho- 
roughly tempered,  like  mortar.  Mr.  Watt's  fire  lute  is  an 
excellent  one,  but  is  more  expensive.  It  is  made  of  finely 
powdered  Cornish  (porcelain)  clay,  mixed  to  the  consistence 
of  thick  paint,  with  a  solution  of  borax,  in  the  proportion  of 
two  ounces  of  borax  to  a  pint  of  hot  water. 

Fat  lute  is  prepared  by  mixing  dry  clay,  in  a  fine  powder, 
with  drying  oil,  so  that  the  mixture  may  form  a  ductile  paste. 
It  should  be  kept  under  cover,  preferably  in  a  greased  blad- 
der. When  this  paste  is  used,  the  part  to  which  it  is  applied 
ought  to  be  very  clean  and  dry,  otherwise  it  will  not  adhere. 
This  lute  is  adhesive,  and  stands  a  pretty  high  heat,  but 


278  LUTE  FOR  COATING  FIRE  VESSELS. 

requires  to  be  fastened  down  vdth.  strips  of  bladder.  Its 
greatest  disadvantage  is  the  diflScultv  of  stopping  holes  which 
may  be  blown  through  it  by  escaping  vapor. 

tead  and  Oil  Lute, — Red  lead  mixed  with  boiled  linseed 
oil  is  excellent  for  sealing  the  joints  of  steam-vessels.  It 
hardens  readily  and  bears  a  high  heat. 

Litte  for  coating  Fire  Vessels. — Faraday  gives  the  follow- 
ing directions  for  luting  iron,  glass,  or  earthenware  retorts, 
tubes,  &c.,  for  furnace  operations.  "\Mien  the  lute  has  to 
withstand  a  very  high  temperature,  it  should  be  made  of  the 
best  Stourbridge  clay  which  is  to  be  made  into  a  paste,  vary- 
ing in  thickness  according  to  the  opinion  of  the  operator.  The 
past«  should  be  beaten  until  it  is  perfectly  ductile  and  uniform, 
and  a  portion  should  then  be  flattened  out  into  a  cake  of  the 
required  thickness,  and  of  such  a  size  as  shall  be  most  man- 
ageable with  the  vessel  to  be  coated.  If  the  vessel  be  a  retort 
or  flask,  it  should  be  placed  in  the  middle  of  the  cake,  and 
the  edges  of  the  latter  raised  on  all  sides,  and  gradually 
moulded  and  applied  to  the  glass ;  if  it  be  a  tube,  it  should 
be  laid  on  one  edge  of  the  plate,  and  then  applied  by  rolling 
the  tube  forward.  In  all  cases,  the  surface  to  be  coated  should 
be  rubbed  over  with  a  piece  of  the  lute  dipped  in  water,  for 
the  purpose  of  slightly  moistening  and  lea%'ing  a  little  of  the 
earth  upon  it ;  if  any  part  of  the  surface  becomes  dry  before 
the  lute  is  applied,  it  should  be  re-moistened.  The  lute  should 
be  pressed  and  rubbed  down  upon  the  glass,  successively  from 
the  part  where  the  contact  was  first  made  to  the  edges,  until 
all  air  bubbles  are  excluded,  and  an  intimate  adhesion  efiected. 
When  one  cake  of  lute  has  been  applied,  and  is  not  large  enough 
to  cover  the  whole  required  surface,  another  must  be  adapted 
in  a  similar  manner.  Great  care  must  be  taken  in  joining  the 
edges,  for  which  purpose  it  is  better  to  make  them  thin  by 
pressure,  and  also  somewhat  irregular  in  form,  and  if  at  all 
dry  they  should  be  moistened  with  a  little  soft  lute.  The 
general  thickness  may  be  about  one-quarter  to  one-third  of 
an  inch. 

Being  thus  luted,  the  vessels  are  afterwards  to  be  placed 
in  a  warm  situation,  over  the  sand-bath  or  near  the  ash-pit, 
or  in  the  sun's  rays.  They  should  not  be  allowed  to  dry 
rapidly  or  irregularly,  and  should  be  moved  now  and  then  to 
change  their  positions. 

To  prevent  cracking  during  desiccation,  and  the  consequent 


MODE  OF  APPLYING  LUTES.  279 

separation  of  the  coat  from  the  vessel,  some  chemists  recom- 
mend the  introduction  of  fibrous  substances  into  the  lute,  so 
as  mechanically  to  increase  the  tenacity  of  its  parts.  Horse- 
dung,  chopped  hay  and  straw,  horse  and  cow-hair,  and  tow 
cut  short  are  amongst  the  number.  "Wlien  they  are  used,  they 
should  be  added  in  small  quantity,  and  it  is  generally  neces- 
sary to  add  more  water  than  with  simple  lute,  and  employ 
more  labor  to  ensure  a  uniform  mixture.  It  is  best  to  mix 
the  chopped  material  with  the  clay  before  the  water  is  put  to 
it,  and  upon  adding  the  latter,  to  effect  the  mixture,  at  first 
by  stirring  up  the  mass  lightly  with  a  pointed  stick  or  fork ; 
it  will  then  be  found  easy  by  a  little  management,  to  obtain  a 
good  mixture  without  making  it  very  moist. 

The  luting  ought  to  be  made  as  dry  as  possible,  consistent 
with  facility  in  working  it.  The  more  wet  it  is,  the  more  liable 
to  crack  in  drying,  and  vice  versa, 

Mr.  Willis  recommends,  when  earthenware  retorts,  &c.,  are 
to  be  rendered  impervious  to  air,  the  following  coating.  One 
ounce  of  borax  is  to  be  dissolved  in  half  a  pint  of  boiling 
water,  and  as  much  slacked  lime  added  as  will  make  a  thin 
paste.  This  composition  is  to  be  spread  over  the  vessel  with 
a  brush,  and  when  dry,  a  coating  of  slacked  lime  and  linseed 
oil  is  to  be  applied.  This  will  dry  sufficiently  in  a  day  or  two, 
and  is  then  fit  for  use. 

Cement  for  Labels. — Gum  tragacanth  boiled  with  hot  water 
makes  the  most  adhesive  paste  for  securing  labels  upon  glass 
or  other  smooth  surfaces.  The  addition  of  a  few  drops  of  oil 
of  turpentine  retards  its  decomposition  and  keeps  it  unaltered 
for  a  long  time. 

Mode  of  applying  Lutes. — Lutes  are  applied  whilst  soft, 
being  adjusted  to  the  joints  by  the  hand.  As  they  become 
dry,  occasional  compression  with  the  fingers  is  necessary  to 
render  them  compact.  So  also  when  any  leaks  occur  they 
must  be  closed  with  fresh  portions  of  lute  smeared  over  and 
pressed  in  by  the  end  of  the  thumb.  When  bladder  or  muslin 
is  to  be  pasted  over  lute,  the  joint  made  with  the  latter  must 
first  have  dried. 

When  the  operation  is  finished  and  the  apparatus  is  to  be 
disconnected,  remove  the  lute  first  with  the  hands.  If,  as  is 
often  the  case  in  the  use  of  hard  lutes  in  fire  processes,  they 
adhere  tenaciously,  then  the  use  of  a  knife,  or  when  the  ves- 
sels are  metallic,  a  chisel  becomes  necessary. 


280  SOLUTION. 


CHAPTER    XIX. 

SOLUTION. 

When  a  substance  added  to  a  liquid  is  wholly  or  partially 
taken  up  by  that  liquid,  it  is  said  to  be  soluble  therein.  The 
liquid  employed  is  termed  the  solvent,  and  its  combination 
with  the  dissolved  particles,  a  solution;  and  if  the  liquid  has 
exerted  its  solvent  power  to  the  fullest  extent,  then  the  solu- 
tion which  it  forms  is  said  to  be  saturated  because  it  can  hold 
no  more. 

The  variable  degree  of  solubility  in  different  liquids  serves 
as  a  distinctive  characteristic  of  bodies,  particularly  those 
which  are  solid. 

Solution  is  either  wholly  mechanical,  or  else  chemico-me- 
chanical.  In  the  first  case  it  is  a  molecular  division  of  a  body, 
or,  in  other  words,  a  diffusion  of  its  particles  in  an  appropriate 
liquid  without  any  alteration  of  its  original  properties,  save 
as  to  form  and  cohesion.  Thus,  for  example,  an  aqueous 
solution  of  sugar  or  salt  yields  the  whole  of  its  charge  by 
EVAPORATION,  and  one  of  sulphate  of  lime  by  the  addition  of 
alcohol,  in  which  it  is  insoluble.  Ethereal  or  spirituous  solu- 
tions deposit  their  dissolved  matter  by  distillation  or  crys- 
tallization; and  some  other  kinds,  that  of  gutta-percha,  in 
chloroform,  for  instance,  by  precipitation  with  ether  or 
alcohol.  When  the  dissolved  particles  are  thus  recoverable 
again  in  an  unaltered  state,  chemically  considered,  their  solu- 
tion may  be  styled  simple. 

In  the  second  case  chemico-mechanical  solution,  in  contra- 
distinction to  that  which  is  purely  mechanical,  is  a  process 
requiring  the  modification  of  a  body  by  chemical  action  pre- 
vious to  its  solution.  Thus,  for  example,  copper,  iron,  or  any 
other  base  or  acid,  insoluble  in  the  ordinary  solvents,  may  be 
readily  taken  up  by  liquid  acids  or  bases.  But  the  liquid 
holds  in  solution  a  newly  formed  body  entirely  dissimilar  to 
the  original  substance  in  properties,  as  appears  when  it  is 
separated.     In  this,  therefore,  consists  the  difference  between 


SOLUTION  : — NEUTRALIZATION.  281 

a  simple  or  mechanical  and  a  chemico-mechanical  solution. 
As  examples  of  this  latter,  iron  may  be  dissolved  in  dilute 
sulphuric  acid,  but  in  the  act  is  transformed  into  copperas : — 
alkalies  are  taken  up  by  acids,  but  become  ialtered  to  salts; 
and  oil  in  being  dissolved  by  potassa  solution  is  changed  into 
soap.  Hence  it  is  that  the  chemical  reaction  is  a  preliminary 
step  requisite  to  promote  simple  solution.  The  point  of  satu- 
ration in  chemical  solution  is  that  at  which  the  two  bodies, 
invariably  of  opposite  properties,  have  combined  in  propor- 
tions adequate  to  neutralization. 

There  are  some  exceptions  to  the  above,  which  refer  to 
certain  instances  in  which  acids  and  alkalies  act  as  mere  sim- 
ple solvents,  and  without  changing  the  original  properties  of 
the  dissolved  substance.  For  example,  acetic  acid  dissolves 
certain  phosphates  and  borates ;  aqua  ammonise  takes  up  car- 
mine ;  potassa  water  the  hydrated  peroxide  of  tin,  and  hydro- 
sulphuret  of  ammonia  the  deutosulphuret  of  iridium. 

Solution  is  one  of  the  most  important  processes  in  chemis- 
try; it  not  only  facilitates  chemical  reaction,  but  allows  the 
separation  of  soluble  from  insoluble  bodies,  or  parts  of  the 
same;  and  consequently  the  purification  of  the  solution  by 
subsequent  filtration,  evaporation,  and  crystallization. 

As  regards  the  power  of  dissolving  the  greatest  number  of 
substances,  water  is  the  first  in  the  rank  of  simple  solvents, 
alcohol  the  next,  and  ether  third.  Then  follow  spirits  of  tur- 
pentine, pyroxylic  spirit,  the  volatile  and  fixed  oils,  chloroform, 
and  a  host  of  other  liquids  suitable  to  particular  substances. 
Of  the  alkalies,  aqua  ammonise  or  potassa  are  most  used ;  the 
former  preferably,  because  of  its  volatility  and  that  of  most 
of  its  salts.  All  of  the  common  acids  are  employed,  though 
some  few  only  are  of  general  application :  such  as  the  muriatic, 
nitric,  sulphuric,  acetic,  and  tartaric. 

When  the  solubility  of  bodies  is  spoken  of,  it  is  in  reference 
usually  to  water,  that  being  the  standard  liquid.  In  testing 
the  solubility  of  a  substance,  it  is,  therefore,  usual  to  com- 
mence with  that  liquid,  and  if  it  fails,  to  proceed  with  the 
next  in  order;  and  always,  for  reasons  below  given,  trying 
the  experiment  at  varied  temperatures,  with  gradually  in- 
creased quantities  if  necessary. 

A  very  convenient  way  of  testing  the  solubility  of  a  sub- 
stance is  by  means  of  a  test-tube.  If  solid,  a  small  portion 
in  powder  is  to  be  introduced  and  covered  with  distilled  water, 
19 


282  SOLUTION ; — means  of  facilitating. 

or  the  solvent  to  be  used,  and  repeatedly  agitated  by  the 
hand,  the  forefinger  closing  the  mouth  (Fig. 
Fig.  251.  251)  to  prevent  the  escape  of  particles.     If 

the  matter  is  wholly  soluble  there  will  be 
no  deposit  at  the  bottom  of  the  tube ;  if  par- 
tially soluble  the  deposit  will  have  decreased 
in  bulk ;  if  totally  insoluble  it  will  occupy  the 
same  space  as  at  first.  To  determine  as  to 
the  two  latter  results,  a  minute  portion  of 
the  supernatant  liquid  is  decanted  and  eva- 
porated in  a  small  platinum  spoon  or  strip  of 
window-glass  over  the  spirit  lamp,  (Fig.  115;) 
if  a  residue  remains  it  indicates  that  matter 
has  been  taken  up. 

When  heat  is  required,  the  lamp  (as  at  Fig.  117)  afibrds  a 
convenient  means  of  application.  The  procedure  in  such  cases 
is  the  same  as  that  above  directed. 

Volatile  matters  can  in  this  way  be  recognized  by  their 
odor  emitted  at  boiling  temperature,  or  else  by  the  taste  which 
they  impart  to  the  liquid,  or  by  some  other  characteristic 
test. 

The  solubility  of  a  gas  may  be  ascertained  by  passing  up  a 
given  volume  of  water,  or  other  fluid,  the  solvent  power  of 
which  is  to  be  determined,  into  a  graduated  tube  filled  with 
mercury  and  inverted,  and  then  passing  in  similarly  measured 
volumes  of  the  gas.  When  absorption  ceases,  by  bringing 
the  interior  and  exterior  levels  nearly  even,  allowing  for  the 
Bmall  column  of  water,  the  remaining  gas  subtracted  from  the 
whole  amount  introduced  will  show  how  many  volumes  have 
been  absorbed;  knowing  the  relative  sp.  gr.  of  the  gas  and 
water,  the  volumes  may  be  calculated  to  weights. 

1.  There  are  certain  conditions  which  greatly  facilitate  the 
solution  of  substances: — 1st,  comminution,  which  increases 
the  extent  of  surface ;  2d,  agitation,  which  promotes  the  fre- 
quent contact  of  all  parts  of  the  surface  with  fresh  portions 
of  solvents ;  3d,  the  freedom  from  impurity  of  both  the  solvent 
and  body  to  be  dissolved.  4th,  it  is  also  influenced  by  the 
quantity  and  state  of  dilution  of  the  solvent ;  5th,  by  the  tem- 
perature; 6th,  by  the  mode  in  which  the  process  is  conducted. 

2.  Agitation  is  efiected  by  stirring  with  glass  rods  when 
the  containing  vessel  is  open  at  the  top.  The  rod  should  be 
rounded  at  the  end  over  the  blow-pipe  flame,  and  to  prevent 


SOLUTION  OF  SOLIDS.  28S 

its  rolling  from  the  table  or  top  of  the  vessel  upon  which  it 
should  be  placed,  may  be  square  instead  of  cylindrical  as  is 
usual.  A  very  convenient  and  effective  mode  of  bringing  all 
portions  of  the  liquid  successively  in  contact  with  the  sub- 
stance to  be  dissolved,  is  to  place  the  latter  in  a  cullendered 
diaphragm  suspended  beneath  the  surface  of  the  liquid.  The 
first  stratum  of  liquid  in  becoming  saturated  increases  its 
density,  and  consequently  descends  and  displaces  a  lower  and 
fresher  portion,  which  being  in  the  same  way  surcharged  in 
its  turn,  gives  way  to  successive  strata,  and  so  the  operation 
continues  until  the  whole  of  the  matter,  or  so  much  as  can  be, 
is  taken  up.  This  mode  keeps  the  substance  in  constant  con- 
tact with  new  portions  of  liquid,  and  is,  in  fact,  a  kind  of 
displacement  process. 

When  flasks  or  bottles  are  used  the  same  effect  may  be 
produced  by  repeated  shaking. 

Trituration  in  a  mortar  and  alternate  decantation  and 
fresh  additions  of  the  solvent  greatly  facilitate  the  solution  of 
solid  substances. 

3.  The  purity  of  the  solvent  is  an  important  consideration, 
for  if  it  contain  foreign  matters  they  may  impart  a  dissolving 
power  which  is  not  inherent  in  the  pure  liquid,  or  diminish 
that  already  possessed  by  it.  Faraday  makes  the  following 
excellent  remarks  upon  this  subject. 

*'  It  is  necessary  that  the  student  be  on  his  guard  respecting 
certain  variations  in  the  solubility  of  bodies  arising  from  the 
presence  of  other  matters.  He  will  continually  find  that 
small  portions  of  substances  generally  considered  as  insoluble 
in  water  will  remain  in  neutral  solutions  when  some  other 
substance  is  present,  or  because  of  slight  mutual  decomposi- 
tion; and  he  will  also  frequently  find  that  matter  usually 
considered  as  readily  soluble,  is  so  with  difficulty  when  in, 
contact  with  substances  with  which  it  is  not  apparently  in 
combination.  Thus  water  boiled  upon  muriate  of  potash  and 
phosphate  of  baryta  will  be  found  to  contain  more  baryta  than 
if  boiled  alone  upon  the  phosphate;  and  on  the  contrary,  if 
oxide  of  iron  and  alumina  be  precipitated  together  from  a 
solution,  it  will  be  found  much  more  difficult  to  dissolve  the 
alumina  by  solution  of  potash  than  if  it  had  been  thrown  down 
alone. 

"  The  alkaline  earths  are  remarkably  soluble  in  solutions  of 
sugar,  and  also,  though  to  a  less  degree,  in  solutions  of  extract 


284  SOLUTION ; — influence  of  temperature. 

and  other  vegetable  matters :  hence  they  are  retained  in  solu- 
tion at  times  in  very  unexpected  situations,  and  might  give 
rise  to  much  uncertainty  in  the  appearances  and  characters 
of  other  substances,  unless  the  experimenter  were  aware  of  the 
general  fact.  Platina  is  not  itself  soluble  in  nitric  acid,  even 
when  spongy  and  in  its  most  comminuted  form,  but  when 
alloyed  in  small  quantities  with  metals  dissolved  by  that  acid, 
it  becomes  soluble  with  them,  and  in  consequence  appears 
now  and  then  in  situations  where  it  is  not  expected.  Tartaric 
acid  or  tartrates  have  an  extraordinary  power  in  rendering 
many  metallic  oxides  soluble,  which  are  not  so  by  other  acids 
without  it;  and  still  more  in  holding  them  in  solution  when 
such  substances  are  added  as  in  ordinary  circumstances  effect 
their  separation.  The  oxides  of  bismuth,  antimony,  tin,  and 
titanium,  are  easily  dissolved  by  acids  when  tartaric  acid  is 
present ;  and  being  present,  ammonia  no  longer  has  the  power, 
upon  its  addition,  of  separating  the  oxides  of  iron,  titanium, 
manganese,  cerium,  cobalt,  nickel,  lead,  antimony,  and  the 
earths,  alumina,  magnesia,  and  yttria,  from  their  solutions, 
and  in  certain  cases  even  potash  or  soda  fails  so  to  do.  Great 
advantage  may  be  taken  of  this  property  occasionally,  but 
sometimes  it  is  equally  disadvantageous  in  preventing  the 
usual  action  of  re-agents.*" 

4.  In  regard  to  the  quantity  and  state  of  dilution  of  a 
solvent,  it  must  be  remembered  that  some  substances  require 
more  of  it  than  others  for  their  solution,  and  that  it  should 
be  in  a  greater  degree  of  dilution.  Therefore,  in  examining 
the  solubility  of  a  body  always  commence  with  small  quanti- 
ties, and  increase  both  quantity  and  strength  gradually  as 
may  be  required. 

5.  Temperature  exerts  a  considerable  influence  in  the  solu- 
tion of  bodies;  and  though  in  a  few  instances,  as  in  the 
solution  of  lime,  magnesia  and  anhydrous  sulphate  of  soda  in 
water,  its  elevation  impairs  the  power  of  the  solvent,  yet  as 
an  almost  universal  rule  it  facilitates  its  action.  The  tem- 
perature must  be  adapted  to  the  nature  of  the  solvent  and  the 
substance  to  be  dissolved,  and  of  the  solution  formed. 

It  may  be  as  well  to  mention  that  the  caloric  rendered 
latent  at  the  moment  of  the  liquefaction  of  a  solid,  which  is 
being  dissolved  in  a  liquid,  causes  a  decrease  of  temperature. 

*  Annales  de  Chimie,  xxiii.  356. 


DIFFERENT  MODES  OF  EFFECTING  SOLUTION.  285 

Solution  in  volatile  liquids  should  be  in  most  cases  performed 
in  the  cold,  and  when  of  small  quantities  in  narrow-necked 
flasks.*  If  heat  is  required,  especially  when  the  vapors  are 
inflammable,  a  retort  or  covered  still  must  be  used;  and  if  the 
distillate  is  valuable,  a  recipient  may  be  annexed  to  receive 
as  much  as  comes  over. 

6.  The  mode  of  efiecting  solution  varies  with  the  substance 
under  process:  Maceration,  Decoction,  Infusion,  Diges- 
tion, Boiling  and  Displacement  have  each  and  all  appro- 
priate application. 

In  ordinary  solution  the  solid  should  be  added  in  portions, 
and  sufficient  interval  allowed  for  the  solution  of  those  in  the 
liquid  before  fresh  are  added.  In  case  of  foaming  or  efierve- 
scence  an  additional  amount  of  fluid  will  produce  a  calm. 

For  solution  in  the  cold  or  at  slightly  warm  temperatures 
jars  of  hard  German  glass,  Fig.  252,  are  very  ap- 
propriate vessels.  The  material  in  powder  is  ^ig-  252. 
added  to  the  fluid  in  the  jar  and  contact  of  fresh 
surfaces  promoted  by  stirring  with  a  glass  rod. 
If  the  liquid  solvent  is  volatile  a  glass  stoppered 
bottle  is  a  convenient  substitute  for  the  jar,  agi- 
tation being  eff^ected  by  shaking  it  to  and  fro. 

Some  volatile  substances  which  are  insoluble 
in  water  under  ordinary  circumstances  are  taken 
up  by  it  in  the  state  of  vapor.  For  this  purpose 
both  should  be  distilled  together. 

When    solutions,   emitting  corrosive  or  dis- 
agreeable fumes,  are  being  made  in  open  vessels 
the  operation  should  be  conducted  under  a  hood,  the  barrel  of 
which  connects  with  the  chimney-flue  so  as  to  ensure  their 
exit. 

The  containing  vessels  should  be  those  which  resist  the  ac- 
tion of  heat,  acid,  alkalies,  and  corrosive  liquids. 

For  making  saturated  solutions  of  most  substances,  ebul- 
lition is  necessary.  For  this  purpose  the  solid  must  be  boiled 
with  the  solvent  until  the  latter  on  cooling  deposits  some  of 
its  charge.     The  cooled  solution  is  then  to  be  filtered. 

*  When  weighed  quantities  are  to  be  transferred  to  a  flask  or  other  narrow- 
mouthed  vessel,  the  use  of  a  funnel  will  prevent  liability  of  loss.  Any  particles 
that  may  adhere  to  the  side  of  the  barrel  can  be  washed  down  with  portions  of 
solvent. 


286  SOLUTION ; — op  liquids  ; — of  gases. 

Metals  in  their  free  state  are  dissolved  one  in  the  other  by 

FUSION. 

Solution  of  Liquids. — Agitation  of  the  liquid  to  be  dissolved 
together  with  the  solvent  generally  effects  solution.  If  upon 
repose  there  are  two  layers,  then  all  the  matter  is  not  taken 
up,  and  that  portion  which  represents  the  solution  must  be 
separated,  and  a  fresh  quantity  of  the  solvent  added.  This 
process  is  to  be  repeated  until  all,  or  as  much  as  possible,  of 
the  liquid  is  dissolved. 

Solution  of  Gases."^ — The  generation  and  solution  of  gases 
are  generally  simultaneous  processes,  and  have  been  fully 
treated  of  at  p.  258.  When  water  is  used  it  must  be  distilled 
and  boiled  to  expel  air.  Viscid  liquids  are  not  less  solvent 
than  others,  but  take  up  the  gas  much  more  slowly.  As  a 
general  rule  the  capacity  of  a  liquid  for  a  gas  is  proportional 
to  its  rarity.     (Berzelius.) 

The  following  table  (from  Gray's  Pharmacopoeia)  of  the 
solubility  of  some  of  the  salts  most  in  use  will  be  found  very 
convenient: — 

*  Liquefaction  and  Solidification  of  Gases. — Faraday  has  succeeded  (Ann.  de 
Chim.  et  de  Phys.  3d  Series.  Vol.  13,  p,  121)  in  liquefying  certain  gases  by 
the  combined  aid  of  pressure  and  refrigeration.  Among  them  are  olefiant  gas, 
fluosilicic  and  hydrochloric  acids.  Alcohol  was  partially  solidified  in  the  same 
manner.  Hydriodic,  hydrobroraic,  and  carbonic  acids,  sulphuretted  hydrogen 
and  ammonia  assumed  well  defined  solid  forms. 

The  author  thus  speaks  for  himself: — "I  sought  in  the  first  place  to  obtain  a 
very  low  temperature,  and  employed  for  this  purpose  Thilorier's  bath  of  solid 
carbonic  acid  and  ether,  placing  it  however  under  the  recipient  of  an  air-pump. 
By  maintaining  a  constant  vacuum,  I  lowered  the  temperature  to  such  a  degree, 
that  the  carbonic  acid  of  the  bath  was  not  more  volatile  than  water  at  the  tem- 
perature of  86°,  for  the  barometer  of  the  air-pump  stood  at  28*2  inches,  the 
external  barometer  being  at  29*4. 

"  This  arrangement  made,  I  joined  together,  by  means  of  cork?  and  stop-cocks 
some  small  glass  and  copper  tubes,  so  that  with  the  aid  of  two  pumps  I  was 
able  to  subject  various  gases  to  a  pressure  of  40  atmospheres,  and  at  the  same 
time  to  submit  them  to  the  intense  cold  obtained  under  the  air-pump,  and  to 
examine  the  resulting  effects.  As  I  expected,  the  cold  produced  several  results 
which  pressure  alone  would  never  have  done,  and  principally  in  the  solidifica- 
tion of  bodies  ordinarily  gaseous." 


SOLUBILITY  OF  SALTS. 


287 


THE  SOLUBILITY  OF  SALTS. 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

Alcohol 

at  60O              at  Boiling  point. 

at  60O     Bt  Boiling  point. 

ALUmNA. 

Undetermined 

Acetate  of        .        .        . 

Ar8eniate  of     . 

Insoluble 

Borate  of 

Uncrystallizable 

Camphorate  of 

0.05 

Lactate  of 

Uncrystallizable 

Muriate  of 

Very  soluble 

100  at  54i° 

Nitrate  of 

Very  soluble 

100 

Oxalate  of 

Uncrystallizable    . 

2.91 

Phosphate  of    . 

Insoluble 

Seleniate  of 

Insoluble 

Sulphate  of      . 

50 

Sulphate  of,  and  Potash 

5.4                         133.33 

Sulphate  of,  and  Soda 

100 

Sulphite  of 

Ihsoluble 

Tartrate  of 

Uncrystallizable    . 

2-91 

Tartrate  of,  and  Potash 

Uncrystallizable 

Tungstate  of    . 

Insoluble 

Urate  and  Lithate  of 

Insoluble 

AMMONIA. 

Very  soluble 

Acetate  of        .         .         . 

Readily  soluble 

Arseniate  of     . 

Soluble 

Binarseniate  of 

Soluble 

Arsenite  of 

Uncrystallizable 

Benzoate  of      . 

Soluble 

Boletate  of 

38 

Borate  of 

8^          .... 

0.416 

Camphorate  of 

1                                  33 

Carbonate  of  (Sesqu 

)       • 

33    {Ure) 
20     (Brande) 

~~ 

Chlorate  of 

Very  soluble 

Chromate  of     . 

Very  soluble 

Citrate  of 

Difficultly  crystallizable 

Ferrocyanide  of 

Very  soluble 

Formate  of 

Soluble 

Hydriodate  of  (or  I 
of  Ammonium) 

odide) 

Very  soluble 

Hydrocyanate  of 

Soluble 

Hydrosulphuret  of    . 

Very  deliquescent 

Hypophosphite  of     . 

Soluble  and  deliquescent 

Hyposulphite  of 

Very  soluble 

- 

lodate  of 

Sparingly  soluble 

Lactate  of 

Uncrystallizable 

Meconate  of     . 

66 

Molybdate  of  . 

Soluble 

288 


SOLUBILITY  OF  SALTS. 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

Alcohol 

at  60°             at  Boilii 

ig  point. 

at  60°      at  Boiling  point. 

AMMONIA. 

" 

J  7.5  at  80°  (°i£)  .900 

Muriate  of  (or  Chloride  of) 

36 

100 

Ammonium)  . 

^ 

^  4.75  do.  \  bL:c  J.  .872 

U.5     do.    l^^)  .834 

Nitrate  of 

50 

100 

19.16 

Oxalate  of 

4.5 

40.84 

Phosphate  of    . 

25    {Brande) 

Biphosphate  of 

Less  soluble 

Phosphite  of     . 

Very  soluble 

Purpurate  of     . 

.0066             much 

more 

Pyrolithate  of  . 

Soluble 

Suberate  of 

Very  soluble 

Succinate  of     . 

Very  soluble 

Sulphate  of 

60     {Brande) 

100 

Sulphite  of 

100     {Ure) 

Tartrate  of 

60.03 

304.7 

2.91 

Tungstate  of    . 

Soluble 

ANTIMONY. 

Soluble     (Ure) 

Acetate  of 

"\ 

Benzoate  of      . 

. 

Soluble     (Ure) 

Tartrate  of 

, 

Very  soluble     {Brande) 

Potassio-tartrate  of 

• 

7 

50 

,     BISMUTH. 
A 

Soluble 

Acetate  of 

'\ 

Arseniate  of     . 

Insoluble 

Benzoate  of 

Soluble 

. 

Sparingly 

Carbonate  of     . 

Insoluble 

, 

Chloride  of 

Deliquescent 

Nitrate  of 

Decomposed 

Phosphate  of    . 

Soluble 

Sulphate  of       . 

Decomposed 

BARYTA. 

A 

5  at  50°           10  at  212^ 
88                                 96 

Acetate  of 

^\ 

• 

Antimoniate  of 

Insoluble 

Antimonite  of  . 

Slightly 

Arseniate  of     . 

Insoluble 

Arsenite  of 

Difficultly 

Benzoate  of 

Soluble 

Borate  of 

Very  sparingly 

Camphorate  of 

Very  sparingly 

Carbonate  of    . 

Very  nearly  insoluble 

Chlorate  of 

25 

Chromate  of     . 

Very  sparingly 

Citrate  of 

Difficultly  soluble 

P^errocyanuret  of 

.0005 

.01 

Hydriodate  of  (or  1 
of  Barium)     . 

odide; 

Very  soluble 

SOLUBILITY  OF  SALTS. 


289 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

^ 

Alcohol 

at  60O             at  Boiling 

point. 

ai  60O     at  Boiling  point. 

BARYTA. 

5  at  50o           10  at  212o 

>v 

~> 

Hydrosulphuret  of    . 

11 

50 

Hypophosphite  of 

Very  soluble 

lodate  of 

.33 

1.6 

Lactate  of 

. 

Soluble 

Lithate  of 

Insoluble 

ri  at  80^  O  ^  r-900 
J  0.29     .     .    1  *  ,'  .848 

Muriate  of  (or  Chloride  of 

} 

36.8 

68.5 

Barium)  (Anhydrous) 

i  0.18     .     .    f  2  1  .834 

1  0.09     .     .  J  ^  (  .817 

*-                   ^w  ^ 

ri.56at80o  r*^  .900 

Muriate  of  (or  Chloride  of 
Barium)  Cryst. 

1^ 

43    {Brande) 

78 

0.43  .  .  ^  .848 
^  0.32  .  .  .<  "o  >.834 
1  0.06     .     .   1   ^ 

Nitrate  of 

5  8.18  at    58.9° 
^35.18  at  214.97° 

Oxalate  of 

Nearly  insoluble 

Phosphate  of    . 

Insoluble 

Phosphite  of     . 

0.25 

Pyrocitrate  of 

.066 

.02 

Sulphate  of 

Insoluble 

Sulphite  of 

Insoluble 

Tartrate  of 

Slightly 

COBALT. 

Soluble 

r 
Acetate  of 

Antimoniate  of 

Soluble 

Arseniate  of     . 

Insoluble 

Borate  of 

Scarcely 

Carbonate  of    . 

Insoluble 

Lactate  of 

.026     {Ure) 

Muriate,  or  Chloride  of 

Very  soluble 

Nitrate  of 

Soluble 

. 

100  at  54^° 

Oxalate  of 

Insoluble 

Sulphate  of       . 

4    (Brande)  . 

. 

Insoluble 

Tartrate  of 

Soluble 

COPPER. 

A 

{Ure) 

20 

Acetate  of 

^\ 

Antimoniate  of 

Insoluble 

Arseniate  of     . 

Insoluble 

Benzoate  of      . 

Slightly 

Borate  of 

Insoluble 

Carbonate  of    . 

Insoluble 

Chlorate  of 

Soluble 

Chromate 

Insoluble 

Citrate  of 

Insoluble 

Ferrocyanide  of 

Insoluble 

Fluoride  of      . 

Soluble 

290 


SOLUBILITY  OF  SALTS. 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

^ 

Alcohol 

ai  60O             at  Boilins:  point. 

at  60O      at  Boiling  point. 

COPPER. 

>v. 

12 

Formate  of       .        .        . 

Hyposulphite  of 

Soluble 

Muriate,  or  Chloride  of    . 

Soluble 

100  at  176'' 

Dichloride  of   . 

Nearly  insoluble 

Nitrate  of          .         .         . 

Deliquescent 

Oxalate  of         .         .        . 

Soluble  ? 

and  Ammonia 

Soluble! 

and  Potassa     . 

Soluble? 

and  Soda 

Insoluble 

Phosphate  of    .        .        . 

Insoluble 

Subnitrate  of    . 

Insoluble 

V 

Sulphate  of       .         .        . 

25                                60 

Disulphate  of   . 

Insoluble 

Trisulphate  of 

Insoluble 

Sulphite  of  Protoxide 

Insoluble 

Sulphate  of  and  Potassa  . 

Soluble 

and  Ammonia 

Soluble 

Ammonio  Subsulphate 

66.6 

Tartrate  of       .         .         . 

Soluble 

Bitartrate  of     .         .         . 

Less  soluble 

Tartrate  of  and  Potassa    . 

Soluble 

GOLD. 

Soluble 

Perchloride  of . 

Protochloride  of 

Soluble 

IRON. 

Soluble 

(                                              ^ 
Acetate  (Prot.) 

Acetate  (Per.)  . 

Uncrystallizable 

Antimoniate  of 

Insoluble 

Arseniate  of  (Prot.)  . 

Insoluble 

Arseniate  of  (Per.)   . 

Insoluble 

Benzoate  of      .        .        . 

Insoluble 

Borate  of          .         .         . 

Insoluble 

Citrate  (Proto.) 

Soluble 

Citrate  (Bi  proto.)     . 

Sparingly  soluble 

Citrate  (Per.)    . 

(  Very  sol  uble  and  uncrys-  ) 
\     tallizable                      \ 

Ferrocyanide  (Prussian  Blue) 

Insoluble 

Fluoride  of       .        .         . 

Insoluble 

Gallate  of  Peroxide  of      . 

Insoluble 

Hyposulphite  of 

Soluble 

Lactate  of  Protox.  of 

Scarcely 

Molybdate  of  Protox.  of  . 

Insoluble 

Protochloride  of 

Soluble 

Perchloride  of 

Very  soluble 

100  at  1760 

Nitrate  of  Protoxide  of     . 

Uncrystallizable 

Nitrate  of  Peroxide  of 

Very  soluble 

Oxalate  of  Protoxide  of    . 

Soluble 

Oxalate  of  Peroxide  of     . 

Scarcely 
Insoluble 

Phosphate  of    . 

SOLUBILITY  OF  SALTS. 


^91 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

^ 

Alcohol 

A 

at  60O             at  Boiling:  point. 

at  GOO      at  Boiling  point. 

IRON. 

Nearly  insoluble 

Phosphate  of  Peroxide  of 

Superphosphate  of   . 

Nearly  insoluble 

Succinate  of  Peroxide  of 

Insoluble 

Sulphate  of  (Cryst.) 

76.238    (Brande) 

333.3 

Sulphate  of  (dry) 

Persulphate  of 

Uncryslallizable 

. 

Soluble 

Hyposulphite  of 

Uncrystallizable 

Persulphate  of  and  Potassa 

Soluble 

Persulphate   of  and   Am-> 
monia    ...          J 

Soluble 

Tartrate  (Proto.)  of  . 

0.25    {Dumas) 

Tartrate  (Per.)  of      . 

Soluble 

Tartrate  of  and  Potassa    . 

Uncrystallizable 

• 

Soluble 

LEAD. 

27     (Bostock) 

29 

Acetate  (Cryst.) 

12.5    (Brande) 

Acetate  (Anhyd.) 

,          ,          , 

, 

Soluble 

Diacetate  of     . 

Soluble 

Antimoniate  of 

Insoluble 

Arseniate  of 

Insoluble 

Benzoate  of      . 

Insoluble 

Borate  of 

Insoluble 

Carbonate  of    . 

Insoluble 

Citrate  of 

Nearly  insoluble 

Chlorate  of 

Soluble 

Chloride  of 

3.33     {.Brande) 

4.5 

Chloride  of  (fused) 

Chromate  of      . 

Insoluble 

Ferrocyanuret  of 

Insoluble 

Gallate  of 

Insoluble 

Iodide  of 

0.08 

0.5 

Hyposulphite  of 

Soluble 

Lactate  of 

Soluble     (Ure) 

Superlactate  of 

Soluble 

Malate  of 

Scarcely 

Molybdate  of   . 

Insoluble 

Nitrate  of 

13 

Dinitrate  of       . 

(  Scarcely  at  60^,  but  much 
\     more  so  at  212° 

Oxalate  of 

Insoluble 

Phosphate  of    . 

Insoluble 

Phosphite  of     . 

Insoluble 

Succinate  of     . 

Insoluble 

Sulphate  of 

Not  absolutely  insoluble 

Sulphite  of 

Insoluble 

Tannate  of 

Insoluble 

Tartrate  of 

Almost  insoluble 

and  Pota 

3sa 

Insoluble       {Berzelins) 

292 


SOLUBILITY  OP  SALTS. 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

•«. 

Alcohol 

at  603             at  Boiling  point. 

at  60°      at  Boiling  point. 

LIME. 

(Kirwan) 

A 

1                                                                                  \ 

r2.4at80°r's    ~).900 
J  4.12  .     .  j  c£  1.848 
1  4-75  .     .  i  ^1"  r.834 

1^4.88.   .  i^'^'j.sn 

Acetate  of       .        .        . 

Soluble 

Antimoniate  of 

Insoluble 

Arseniate  of     . 

Insoluble 

Arsenite  of       .         .         . 

Difficultly  soluble 

Benzoate  of      .        .        . 

Sparingly  soluble 

Borate  of          .         .         . 

Very  difficultly 

Carbonate  of  (Anhyd).      . 

Insoluble 

Chlorate  of       .         .         . 

Very  soluble 

Soluble 

Chromate  of     .        .         . 

Soluble 

Citrate  of          .         .        . 

Nearly  insoluble 

Fluoride  .... 

Insoluble 

Hypophosphite  of     . 

<  Solubility  nearly   equal 
\     at  all  temperatures 

Hyposulphate  of 

40.65     (Brande)        150 

Hyposulphite  of 

Very  soluble 

lodate  of           ... 

20                               100 

Iodide  of  Calcium     . 

Deliquescent 

Malate  of          .         .         . 

.66                             1.53 

Molybdate  of   . 

Insoluble 

r200  at  32° 

J  400  at  60° 

Muriate,  (or  Chloride   of) 
Calcium)        .        .          J 

1  almost  any  quantity  at 

i      220° 

Nitrate  of         .         .         . 

S5          .... 

161.66 

Oxalate  of 

Insoluble 

Phosphate  of    . 

Insoluble 

Biphosphate  of 

Soluble 

Subphosphate  of 

Almost  insoluble 

Succinate  of     . 

Difficultly  soluble 

Sulphate  of       .        .        . 

0.301  at  50° 

Sulphite  of       .         .        . 

12.5 

Tartrate  of       . 

;  Nearly  insoluble  at  60° 
'[     but  .16  at  212° 

Tungstate  of     . 

Insoluble 

LITHIA. 

>^ 

Deliquescent 

Acetate  of        .         .         . 

Bicarbonate  of 

Slightly  soluble 

Borate  of           .         .         . 

Soluble 

Carbonate  of    . 

1            .... 

Insoluble 

Chloride  of  Lithium 

Very  deliquescent 

Chromate  of      .         .         . 

Very  soluble 

Citrate  of          .        .         . 

Very  difficultly  soluble 

Nitrate  of          .         .         . 

Very  deliquescent 

Oxalate  of         .         .         . 

Very  deliquescent 

Binoxalate  of    . 

Less  soluble 

Phosphate  of    . 

Insoluble 

Sulphate  of      .        .        . 

Soluble 

SOLUBILITY  OF  SALTS. 


293 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

^ 

Alcohol 

at  60O              at  Boiling  point. 

at  60°     at  Boiling  point. 

LITIil 
, ^■ 

Tartrate  of 

A. 

^ 

Easily  soluble 

and  Potassa    . 

Easily  soluble 

and  Soda 

Easily  soluble 

MAGNESIA. 
A. 

Very  soluble 

(                                             \ 
Acetate  of        .         .         . 

Arseniate  of     . 

Deliquescent 

Arsenite  of 

Difficultly  soluble 

Benzoate  of 

Soluble 

Borate  of 

Insoluble 

Carbonate  of    . 

Very  slightly 

Chlorate  of 

Very  soluble 

f50                                  547 

Chloride  of  Magnesium     . 

200    (Brande) 

^'50at80O  fSp.gr.j  .817 

., 

i.2125...  (  Spts.  j  .900 

Chromate  of     .        . 

Very  soluble 

Citrate  of          .         .         . 

Difficultly  soluble 

Iodide  of  Magnesium 

Soluble 

Malate  of          .         .         . 

3.56    {Brande) 

Molybdate  of    . 

6.66                          8.35 

^Nearly    insoluble    in 

Nitrate  of         .         .        . 

100       ...        . 

<      pure  alcohol 
(11  sp.gr.  .840 

Oxalate  of         .        .         . 

Nearly  insoluble 

Phosphate  of    . 

6.66 

and  Ammonia 

Sparingly  soluble 

Succinate  of     .         . 

Uncrystallizable 

Sulphate  of  (dry) 

33.192                     73.57 

Sulphate  of  (cryst.)  . 

68.042                    150.71 

1  at  80°        {Kirwan) 

and  Ammonia 

Soluble 

and  Potassa  . 

Soluble 

and  Soda 

33.3 

Sulphite  of       .         .         . 

5 

and  Ammonia 

Difficultly  soluble 

Tartrate  of       .         .         . 

Insoluble 

Tungstate  of    . 

Soluble 

I 

MANGANESE. 

3 

f                                    ^ 
Acetate  of        .         .         . 

Soluble 

Ammonio-chloride  of 

Soluble 

Ammonio-sulphate  of 

Soluble 

Antimoniate  of 

Moderately  soluble 

Arseniate  of     . 

Insoluble 

Benzoate  of 

Deliquescent     {Brande) 

Carbonate  of 

Insoluble 

Chromate  of 

Soluble 

Nitrate  of 

Very  soluble 

Soluble 

Oxalate  of 

Insoluble 

Phosphate  of 

Nearly  insoluble 

Succinate  of 

1     {Ure) 

294 


SOLUBILITY  OP  SALTS. 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

^ 

Alcohol 

at  60°             at  Boiling  point. 

at  60°     at  Boiling  point. 

MANGANESE. 

>v 

Sulphate  of       .        .        . 

81     (Ure) 
60    {Brande) 

Hyposulphate  of 

Deliquescent 

Sulphite  of       .         .        . 

Insoluble 

Tungstate  of    . 

Insoluble 

MERCURY. 

TV. 

0.16    (Braconnot) 

Acetate  of  (Prot.)      . 

Acetate  of  (Per.)       . 

Readily  soluble 

Arseniate  of     . 

Insoluble 

Benzoate  of      .        .         . 

Insoluble 

Borate  of          .         .        . 

Insoluble 

Bichloride  of    . 

6.25     {Brande)         33.3 

42.6                     85.2 

r     10.74  at  50° 
J  Sprts.  sp.  gr.  .915 
^      43.66  at  50° 

I^Sprts.  sp.  gr.  .818 

Chloride  of       .        .        . 

.00833  at  212°   {Dumas) 

{Graham) 

Chromate  of     . 

Insoluble 

Citrate  of           .         .         . 

Insoluble 

Bicyanuret  of  . 

54 

Fluoride  of       .        .        . 

Soluble 

Molybdate  of   . 

Very  sparingly 

Nitrate  (Prot.)  . 

(Soluble  and  decomposed 
I     by  excess 

Nitrate  of  (Per.) 

Do.               do. 

Oxalate  of  (Proto.)    . 

Scarcely 

Oxalate  of  (Per.) 

Insoluble 

Sulphate  of  (Proto.) 

0.20                           0.33 

Sulphate  of  (Per.)      . 

Decomposed 

Sulphate  of  (Sub.)     . 

.005                           0.33 

Tartrate  of       .        .        . 

Insoluble 

and  Potassa     . 

Soluble 

- 

NICKEL. 

Acetate  of        .         .         . 

Very  soluble 

Arseniate  of     . 

Soluble     {Ure) 

Carbonate  of    . 

Insoluble 

Chloride  of       .         .        . 

Soluble  in  hot  water 

Nitrate  of  Protox.     . 

50          .        .        .        . 

and  Ammonia 

Soluble 

Oxalate  of         .         .         . 

Insoluble 

Phosphate  of    . 

Nearly  insoluble 

Sulphate  of       .         .         . 

33.3                       185.71 

and  Ammonia 

25 

and  Potassa    . 

11.1 

and  Iron 

Soluble 

Tartrate  of       .        .        . 

Very  soluble 

Soluble 


SOLUBILITY  OP  SALTS. 


295 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

Alcohol 

at  60°             at  Boiling  point. 

at  60O     at  Boiling  point. 

PLATINUM. 

Soluble 

Protochloride  of 

^ 

(Easily  soluble,  also  in 
I     Ether 

Perchloride  of  . 

Soluble 

Protochloride  of 

and  Ammonium 

1 

Soluble 

. 

Insoluble 

and  Potassium 

Soluble 

. 

Insoluble 

and  Sodium 

Uocrystallizable    . 

. 

Very  soluble 

Bichloride  of    . 

and  Ammonium 

( 

Very  sparingly 

and  Potassium 

Very  sparingly 

and  Sodium 

Soluble 

. 

Soluble 

and  Barium 

Soluble 

Protonitrate  of 

Soluble 

Pernitrate  of     . 

Soluble 

Protosulphate  of 

Soluble 

Persulphate  of 

Very  soluble 

(Very  soluble,  also  in 
I     Ether 

POTASS  A. 

100        ..        . 

Acetate  of 

^ 

2oa 

Ammonio-oxalate  of 

Soluble 

Ammonio-suiphate  of 

13 

Ammonio-tartrate  of 

Very  soluble 

Antimoniate  of 

Slightly 

Antimonite  of  , 

Soluble 

Arseniate  of 

Uncrystallizable    . 

. 

a.75 

Binarseniate  of 

18.86  at  40° 

. 

Insoluble 

Arsenite  of 

Uncrystallizable 

Benzoate  of 

Very  soluble 

Bibenzoate  of  . 

10 

Borate  of 

Soluble 

Camphorate  of 

1 

25 

Carbonate  of     . 

100 

Bicarbonate  of 

25 

83 

Chlorate  of 

6.03               60  at  ISSi* 

Chromate 

48                     extremely 

Insoluble 

Bichromate  of  . 

10                  much  more 

Citrate  of 

Very  soluble 

Columbate  of   . 

Uncrystallizable 

Ferrocyanide  of 

33.3 

100 

Iodide  of  Potassium 

143  at  6.5°     (G.Lussac) 

Sparingly 

lodate  of 

7.14    {Brande) 

Molybdate  of   . 

Soluble 

Chloride  of  Potassium 

(29.21  at    66.83°  ) 
^59.26  at  229.28°  J 

(  29.31  at    64°) 

• 

f2  083 

1  4  62  at  80°  C  °  «  -)   .900 

1.66     .     .    ■!&?>■  .812 

10.38     .    .     i^j:}  .834 

Nitrate  of 

;  236.45  at  207°  V 
^285.      at  238°) 

• 

2.083 

Oxalate  of 

• 

(50     {Ure)      . 
1 30    {Brande) 

\ 

(  2.76  at  80O  Sp.  gr.  .900 
( 1    .        .of  Sprls.  .872 

Binoxalate  of   . 

. 

{\0  Brande)     {Ure  100) 

296 


SOLUBILITY  OF  SALTS. 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

j^ 

Alcohol 

at  60°             at  Boiling  point. 

at  6OO      at  Boiling  point. 

POT  ASS  A. 

TV. 

66.66 

Quadroxalate  of 

2.91 

Phosphate  of    . 

Difficultly  soluble 

Diphosphate  of 

Soluble  in  hot  water 

Biphosphate  of 

Very  soluble 

Hypophosphite  of     . 

Very  deliquescent 

Very  soluble 

Hyposulphate  of 

[Difficultly  soluble  at  60° 
'[     readily  at  212° 

Hyposulphite  of 

Deliquescent 

and  Silver 

Difficultly 

Succinate  of     .        .        . 

Very  soluble 

Sulphate  of       .        .         . 

5  10.57  at    54° 
)26.33at214° 

Bisulphate  of    . 

5   50  at    40° 
{200at220° 

Sulphite  of        .        .        . 

100 

Tartrate  of 

100        ...        . 

0.416 

Bitartrate  of     .        .        . 

1.05                           6.66 

2.91 

Tartrovinate  of 

10                any  quantity 

Tungstate  of    . 

Uncrystallizable 

Nitro-tungstate  of    . 

{Ure)     5 

SILVER. 

Very  difficultly  soluble 

Acetate  of        .        .        . 

Arseniate  of     .         .         . 

Insoluble 

Arsenite  of       .         .        . 

Insoluble 

Borate  of          .         .         . 

Difficultly  soluble 

Chlorate  of       .         .         . 

25    (Chenevix) 

Chromate  of     . 

Very  slightly 

Citrate  of           .         .         . 

Insoluble 

Molybdate  of    . 

Insoluble 

Chloride  of  (Fused) 

Insoluble 

Nitrate  of  (Cryst.)     . 

100                             200 

25 

Oxalate  of         .         .         . 

Insoluble 

Phosphate  of    . 

Insoluble 

Succinate  of     .         .         . 

Soluble 

Sulphate  of       .         .         . 

1.15 

Sulphite  of        .         .         . 

Very  little  soluble 

Hyposulphite  of 

Soluble 

and  Potassa 

Difficultly  soluble 

Tartrate  of       .         .         . 

Soluble 

and  Potassa    . 

Soluble 

SODA. 

35                                150 

Acetate  of        .         .         . 

Arseniate  of     .        .        . 

510     (Thompson) 
125     (Ure) 

♦ 

Binarseniate  of 

Soluble 

and  Potassa 

Soluble 

Benzoate  of      .         .        . 

Very  soluble 

Biborate  of       .         .         . 

8.033                            50 

Carbonate  of    . 

50                                100 

SOLUBILITY  OF  SALTS. 


297 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

Alcohol 

at  60O             at  Boiling  point. 

at  60O      at  Boiling  point. 

SODA. 

7.6 

Bicarbonate  of 

Chlorate  of 

33.3       .... 

Sol.  in  sp.  rect. 

Chromate  of     . 

Very  soluble 

Sparingly 

Citrate  of 

100  or  more     (Brande) 

Iodide  of  Sodium      . 

173 

lodate  of  . 

7.3         . 

Insoluble 

Molybdate  of   . 

Soluble 

Muriate  of  (or  Chloride  of) 
Sodium)         .         .          5 

Equally   soluble   at   all) 
temperatures  {Berz.)^ 
r  33.3  at    60»)     „,  «,.,c 
100     at  123^  J    ^""^^ 

(.0.5    .    .     i  Spts.  , 

1.900 

-.872 
1  834 

50     at    60°       Berzel. 

r 

.95S 

73     at    32°)     {Gay 

J  10.5at80O  (Sp.gr.) 

.900 

Nitrate  of         .        .        . 

<  173     at2l2°j   Lussac) 

6    .    .    .         of 

.872 

80     at    32°i 

io.38    .    .    (  Spts. 

.834 

22.7  at    50°  I    ^^^^ 
55     at    61°  >  ^^'"^ 

^218.5  at  246"J 

Oxalate  of         .        .        . 

Sparingly  soluble 

Phosphate  of    . 

25                                 50 

and  Ammonia 

Soluble 

Biphosphate  of 

Very  soluble 

Hypophosphite  of     . 

Very  soluble 

Very  soluble 

Succinate  of     . 

Soluble 

Sulphate  of  (Cryst.)  . 

5   48.28  at  64° 
•  322.12  at  91° 
(16.73  at    64°)      ,^^^, 
)50.65at    91°[    j^^^) 
(42.65  at  217°  S    ■^"««"^> 

Sulphate  of  (dry) 

Insoluble 

Hyposulphate  of 

41.6                              91 

Insoluble 

Bisulphate  of   . 

50 

Sulphate  of  and  Ammonia 

Soluble 

Sulphite  of       .         .         . 

25 

Hyposulphite  of 

Deliquescent 

Insoluble 

Tartrate  of       .         .         . 

56.37     {Thomson) 

Insoluble 

and  Potassa    . 

20 

(Sol.  in  sp.  rect., 

but 

Tartrovinate  of 

Soluble 

}    sparincrly  in  absolute 

(    alcohol 

Tungstate  of    . 

25                                50 

STRONTIA. 

(0.625  at  60O) 
•  5  at  212°      5      ^^'^^^ 
2                                   50 

Hydrate  of        .         .         . 

Acetate  of 

Very  soluble 

Arseniate  of     . 

Sparingly  soluble 

Arsenite  of 

Sparingly  soluble 

Borate  of 

0.76 

Carbonate  of     . 

0.0651  at2123 

Chlorate  of 

Very  soluble 

SoluMe 

Chloride  of  Strontium 

50          .         .         .         ., 

Soluble 

Chromate  of     . 

Insoluble    {Brande) 

- 

Citrate  of 

Soluble 

20 


298 


SOLUBILITY  OF  SALTS. 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

j^ 

Alcohol 

at  60O              at  Boiling  point. 

at  60O      at  Boiling  point. 

STRONTIA. 

J\. 

25 

Ferrocyanuret  of      . 

Iodide  of  Strontium 

Soluble 

lodate  of          ... 

25 

Nitrate  of         .        .         . 

113 

Oxalate  of         .        .         . 

0.52 

Phosphate  of    . 

Insoluble 

Phosphite  of     . 

Soluble 

Hypophosphite  of    . 

Very  soluble 

Succinate  of     .         .         . 

Soluble 

Sulphate  of       .        .        . 

0.026  at  212o 

Hyposulphite  of 

20     {Gay  Lussac) 

Insoluble 

Hyposulphate  of 

22.22                       66.66 

Tartrate  of       .        .        . 

0.67  at  170° 

TIN. 

Soluble 

Acetate  of        .        .        . 

Arseniate  of     .        . 

Insoluble 

Borate  of          ... 

Insoluble 

Nitrate  Proto.  of 

Uncrystallizable 

Nitrate  Per.  of 

Scarcely 

Oxalate  of         .        .         . 

Soluble 

Phosphate  of    . 

Insoluble 

Succinate  of     .        . 

Soluble 

Sulphate  Proto.  of    . 

Crystallizable 

Sulphate  Per.  of 

Uncrystallizable 

Tartrate  of       .        .        . 

Soluble 

and  Potassa    . 

Very  soluble 

ZINC. 

Very  soluble 

Acetate  of        .         .         . 

Antimoniate  of 

Very  sparingly 

Borate  of          .        .         . 

Insoluble 

Chromate  of     . 

Sparingly 

Citrate  of          .         .        . 

Scarcely 

Chlorate  of       .         .        . 

Very  soluble 

Chloride  of       .         .        . 

Very  soluble 

100  at  54io 

Iodide  of          ... 

Soluble 

lodate  of          .        .        . 

Difficultly  soluble 

Lactate  of         .         .         . 

2     (Ure) 

Nitrate  of         .         .         . 

Deliquescent 

Molybdate  of   . 

Insoluble 

Oxalate  of         .        .        . 

Nearly  insoluble 

Phosphate  of    . 

Uncrystallizable 

Succinate  of     .         .        . 

Soluble 

Sulphate  of       .         .         . 

140    {Dumas) 

Sulphite  of 

81.81  at  220^ 

Insoluble 

Hyposulphite  of 

Soluble 

Soluble 

Sulphate  of  and  Nickel     . 

33.33 

Tartrate  of        .         .         . 

Difficultly  soluble 

Tartrovinate  of 

Soluble 

Sparingly  soluble 

Trisulphate  of 

Soluble 

SOLUBILITY  OF  ACIDS,  BASES,  ETC. 
SOLUBILITY  OF  ACIDS,  BASES,  &c. 


299 


Solubihty 

ill  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

Alcohol 

at  GOO 

at  Boilinf?  point. 

at  60O      at  Boiliii":  point. 

ACID. 

A. 

Arsenious 

Vitreous  . 

1.7S 

(Graham' 

9.68 

Opaque     . 

2.9 

(Graham)  11.47 

Benzoic    .... 

.50 

Boracic     .... 

3.9 

33.3 

20  at  176^     (Henry) 

Citric         .... 

133.33 

200 

Soluble 

Gallic        .... 

5 

33.33 

Oxalic  (Cryst.)  . 

11.5 

Succinic  (Cryst.) 

4 

33.33 

74  at  1763 

Tartaric    .... 

150     (Brande) 

200 

Soluble 

Brucia       .... 

.1177 

0.2 

Soluble 

Cinchonia 

Insoluble 

0.04 

Partially  soluble 

Morphia    .... 

Nearly 

insoluble 

1 

4. 

Quinia       .... 

Nearly 

insoluble 

0.5 

Very  soluble 

Strychnia 

0.04    {Graham) 

0.15 

C5.  sp.  grr.  of  spts.  870 
X     (Duflos). 
75  at  176* 

Camphor 

0.229 

. 

. 

Cane  Sugar 

200 

• 

• 

CHAPTER   XX. 


MACERATION.  —  INFUSION.  —  DECOCTION.  —  DIGESTION.  —  BOIL- 
ING.— DISPLACEMENT. 

Maceration. — The  soaking  or  steeping  of  a  substance  in 
a  liquid,  at  the  ordinary  temperature,  is  termed  maceration. 
It  is  almost  exclusively  applicable  to  organic  substances, 
being  most  frequently  resorted  to  as  a  means  of  hastening  and 
facilitating  the  after  solution  of  the  extractive  parts  of  hard, 
compact  or  impervious  wood,  roots,  stems  and  leaves  by  the 
more  active  methods  of  displacement  or  of  ebullition.  It 
is  employed  when  the  soluble  principles  are  alterable  by 
heat:  and  is  also  made  use  of  to  effect  the  solution  of  a  sub- 
stance containing  several  principles,  the  solubility  of  which 
varies  with  the  temperature  applied,  as  it  leaves  those  which 


300  SOLUTION. — INFUSION. — DECOCTION. 

are  not  taken  up  in  the  cold  to  be  acted  upon  by  the  aid  of 
heat.  Thus,  for  example,  in  the  treatment  of  most  vegetable 
substances,  starch  which  is  generally  present  and  is  only  solu- 
ble at  the  boiling  point  of  water,  will  remain  untouched,  while 
all  other  principles  soluble  without  heat  can  be  separated 
from  it. 

The  mode  of  performing  the  process  is  merely  to  place  the 
solvent  and  the  substance  to  be  dissolved,  together  in  a  vessel, 
and  to  allow  them  to  remain  a  longer  or  shorter  time,  accord- 
ing to  the  nature  of  the  substance.  For  ordinary  purposes  a 
loosely  covered  pan  of  blue  stone-ware  is  very  convenient. 
In  delicate  operations  a  beaker  glass.  Fig.  254,  or  solution  jar, 
Fig.  252,  is  more  appropriate.  When  the  solvent  is  volatile, 
a  wide  mouthed  stoppered  bottle  may  be  used. 

Infusion. — This  process  is  likewise  applicable  almost  solely 
to  organic  substances.  Instead,  however,  of  the  solid  remain- 
ing in  contact  for  a  length  of  time  with  the  solvent,  the  latter 
is  first  heated  to  boiling  and  then  poured  upon  the  former. 
After  having  cooled,  the  liquid  may  be  decanted  or  pressed 
out— p.  320,  Fig.  276. 

This  mode  is  used  for  the  exhaustion  of  flowers,  leaves, 
roots,  seeds  and  other  substances  of  delicate  texture,  which 
are  easily  penetrable  and  readily  yield  their  soluble  matters ; 
and  especially  for  the  purpose  of  extracting  volatile  ingre- 
dients. The  heat  applied  to  the  solvent  increases  its  energy; 
but  as  the  material  is  only  in  contact  for  a  limited  time,  the 
interval  between  the  commencement  and  completion  of  the 
operation  is  not  sufficient  to  affect  the  material  or  solution, 
even  though  one  or  more  of  its  components  are  alterable  by 
heat. 

In  pharmaceutical  operations,  this  process  is  generally  con- 
ducted in  cast  iron  flask-shaped  vessels  with  handles,  ena- 
melled on  the  inside  and  fitted  with  a  tight  cover,  which  is  to 
be  kept  in  its  place  from  the  addition  to  the  cooling  of  the 
solvent.  For  small  operations,  a  beaker  glass  covered  with 
a  capsule,  or  a  yellow  earthenware  stew  pan  with  lip  and 
cover,  such  as  can  be  had  at  the  crockery  shops,  are  admirably 
adapted. 

Decoction. — This  mode  of  solution,  which  is  so  important 
to  the  Pharmaceutist,  is  chiefly  employed  for  the  purpose  of 
exhausting  those  vegetable  substances,   the  components   of 


SOLUTION  BY  DIGESTION.  301 

which  will  not  readily  yield  to  other  means.  It  is  merely  an 
extension  of  the  last  process,  and  consists  in  that  contact 
of  the  material  to  be  dissolved  with  a  hot  solvent  in  a  covered 
vessel,  which  is  continued  until  all  soluble  matter  is  taken  up. 
Most  volatile  matters  are  expelled  by  decoction;  but  those 
which  are  insoluble,  save  by  prolonged  action  of  heat,  are 
dissolved  or  suspended,  as  it  were,  by  favor  of  other  principles 
present. 

Decoction  is  only  used  with  liquid  solvents  which  are  not 
decomposable  by  heat. 

In  all  of  the  preceding  processes,  as  well  also  in  others  in 

Fig.  253. 


which  solid  vegetable  matter  is  subjected  to  the  solvent  action 
of  liquids,  the  cullendered  ladle,  Fig.  253,  of  tinned  wire  is 
most  useful  for  transferring  the  residue  to  the  press,  Fig.  276, 
for  removal  of  any  retained  liquid. 

Digestion. — This  mode  of  solution  differs  from  maceration 
in  requiring  the  assistance  of  heat,  and  consists  in  exposing  a 
body  to  the  prolonged  action  of  a  liquid  in  a  covered  vessel,  at 
any  temperature  between  90°  F.  and  several  degrees  less  than 
the  boiling  point  of  the  solvent.  The  method  of  heating 
varies  with  circumstances,  and  can  be  by  a  gentle  fire,  or  by 
the  sand,  steam,  water  or  saline  Bath,  as  the  nature  of  the 
operation  requires. 

In  analysis,  glass  or  platinum  vessels  are  used;  but  in  less 
important  operations  those  of  other  materials  are  more  con- 
venient and  economical. 

A  very  important  advantage  of  digestion  is,  that  it  allows 
the  perfect  solution  of  all  soluble  portions  of  a  substance, 
without  modifying  the  nature  of  the  solvent.  It  is  especially 
useful  for  the  decomposition  of  ores,  minerals  and  other  sub- 
stances difficultly  acted  upon  by  acids  or  other  solvents,  and 
also  for  effecting  the  synthesis  of  compounds  requiring  a  long- 
continued  heat.  Moreover,  it  is  very  available  in  preparing . 
alcoholic  and  aqueous  solutions,  medicinal  oils  and  other  phar- 
maceutical products. 


302 


SOLUTION  BY  DIGESTION. 


Fig.  254. 


In  analytic  operations,  digestion  is  performed  in  beaker 
glasses.  These  are  bell-shaped  vessels, 
Fig.  254,  of  Bohemian  glass,  and  uniformly 
thin  throughout,  so  as  to  support  a  con- 
siderable elevation  of  temperature.  The 
glass  must  be  well  annealed,  hard  and  free 
from  lead,  so  as  to  resist  the  action  of 
acids.  These  vessels  come  in  nests  of  dif- 
ferent numbers.  Their  size  varies  gra- 
dually upwards  from  an  ounce  in  capacity 
to  a  gallon. 

The  substance  to  be  acted  upon,  in  a 
state  of  fine  powder,  is  transferred  to  the 
glass,  which  must  be  perfectly  clean,  and  is  then  mixed  with 
the  proper  quantity  of  acid  or  other  liquid  by  shaking  the 
glass  after  the  addition,  or  by  the  use  of  a  glass  stirrer, 
taking  care,  however,  in  this  last  instance,  if  for  analysis,  to 
wash  off  adhering  particles  previous  to  its  withdrawal,  with  a 
little  fresh  solvent.  The  glass  is  then  to  be  covered  with  a 
square  of  window  glass  (free  from  lead),  a  porcelain  capsule 
or  watch  glass,  whichever  is  most  convenient,  so  that  the 
volatilized  vapors  condensing  upon  their  bottoms  may  fall 
back  again  into  the  vessel. 

If  the  glass  is  small,  it  may  be  directly  heated  over  the 
lowered  flame  of  a  gas  or  spirit  lamp.  Figs.  27, 119,  cautiously 
and  gradually  heightened  as  the  glass  be- 
comes heated.  To  modify  the  action  of  the 
flame  and  diminish  the  danger  of  fracture 
of  the  glass,  a  fine  wire  gauze  5,  for  the  diffu- 
sion of  the  heat,  may  be  interposed  between 
its  bottom  and  the  flame.  Fig.  255  repre- 
sents a  digestion  in  a  beaker-glass  a,  over  a  gas 
lamp  c.  For  larger  vessels  a  Sand  Bath  must 
be  used. 

Thin  flat  bottomed  flasks  with  narrow 
necks  and  smooth  tops.  Fig.  256,  made  of 
hard  glass,  free  from  lead,  are  sold  specially 
for  this  purpose;  but  the  common  sweet  oil 
or  Florence  flasks  are  much  more  economi- 
cal and  equally  convenient  for  operations 
adapted  to  their  capacity.  When  it  is  im- 
portant that  not  even  a  drop  of  substance 


SOLUTION. — DIGESTION  UNDER  PRESSURE. 


303 


shall  be  lost,  as  in  analytic  operations,  the  digesting  flask 
should   have  the  form   shown  in  Fig.  257.      The  body  is 


Fig.  256. 


Fig.  257. 


pear-shaped,  with  flat  bottom,  and  gradually  tapers  towards 
the  mouth,  which  is  lipped  to  facilitate  the  pouring  of  the 
contents. 

Digestion  on  a  small  scale  with  inflammable  liquids,  must 
always  be  eifected  by  the  sand  bath,  so  as  to  avoid  danger 
of  explosion  from  ignition  of  vaporized  particles.  The  Sand 
Bath  may  then  be  heated  over  the  lamp,  as  at  Fig.  119;  and 
in  large  operations  by  the  small  charcoal  furnace,  as  at  Fig. 
87. 

A  digestion  apparatus,  of  Berlin  porcelain,  adapted  for  a 
water  bath,  is  shown  in  Fig.  258.  Its 
dimensions  are  7  inches  in  height,  and  4 
inches  in  diameter,  the  capacity  being  about 
40  ounces.  The  projection  h,  is  a  flange 
for  its  support  in  the  bath;  a,  the  socket 
for  a  wooden  handle,  and  c,  a  section  of 
the  cover.  These  vessels,  made  also  of 
other  sizes,  are  very  convenient  in  pharma- 
ceutical operations,  for  the  digestion  of  or- 
ganic matters,  especially  those  of  vegetable 
origin. 

Digestion  under  Pressure. — The  solvent  power  of  water 
may  be  greatly  increased  by  presenting  it  to  the  substance  in 
the  state  of  vapor.  This  property  afibrds  the  advantage  of 
making  aqueous  solutions  of  highly  obstinate  substances.  The 
appropriate  apparatus  is  termed  a  digester.  That  which 
Papin  used  for  exhausting  bones  of  their  gelatin,  consisted  of 
a  strong  hemispherical  plate  iron  or  copper  pan  of  small  size, 


Fig.  258. 


piMjn 


ic 


304 


SOLUTION. — D  ARCET  S  DIGESTER. 


with  a  self-keyed  lid  smoothly  ground  at  the  edges,  which 
becomes  steam-tight  by  turning  it  around  under  clamps  or 
ears  at  the  side.  Being  thus  tightly  adjusted,  after  having 
received  its  charge,  all  steam  is  confined,  save  that  which 
esqapes  by  the  safety  valve  placed  at  the  top  for  the  preven- 
tion of  explosion.  The  lever  attached  to  the  valve  allows  the 
regulation  of  pressure  according  to  the  amount  of  weight 
applied. 

The  efficacy  of  digesters  is  owing  to  the  boiling  point  of 
fluids  being  increased  by  pressure.  When  the  above  vessel  is 
heated,  the  steam  generated  and  filling  its  upper  and  vacant 
portion,  exerts  a  pressure  upon  the  surface  of  the  liquid  be- 
neath, and  by  thus  retarding  further  ebullition,  causes,  to  a 
certain  extent,  an  accumulation  of  heat  therein. 

In  large  operations,  D'Arcet's  apparatus  (see  Encyclopedia 
of  Chemistry,  article  Gelatin)  is  much  used.  It  is  shown  in 
Figs.  259  and  260.  Our  description  refers  to  the  extraction 
of  gelatin  from  bones  by  water  in  a  state  of  tense  vaporiza- 
tion. 


Fig.  260. 


Fig.  259  is  a  vertical  section  of  the  apparatus.     A  is  an 
hermetically  closed  cast-iron  cylinder,  into  which  the  steam 


SOLUTION. — d'ARCET'S  DIGESTER.  305 

is  conducted ;  a  the  main  steam-pipe ;  h  a  vertical  pipe  con- 
veying the  steam  into  the  cylinder  K\  c  c  branch-pipes  leading 
the  steam  to  the  bottom  of  the  cylinder;  d  a  stopcock  upon 
the  pipe  5,  for  regulating  the  entrance  of  the  steam  into  the 
interior  of  the  cylinder.  (The  tubes  and  the  cylinder  should 
be  wrapped  around  with  woolens,  so  as  to  retain  their  heat 
and  prevent  their  cooling.)  e  is  the  stopcock  for  the  discharge 
of  the  gelatinous  solution ;  /  the  cover  of  the  cylinder,  which 
is  fastened  to  the  cylinder,  so  as  to  prevent  the  escape  of  any 
of  its  contents ;  g  a  tubulure  in  the  cover  for  the  reception  of 
a  thermometer;  A  a  tub  to  receive  the  solution  as  it  is  formed; 
i  a  gutter  for  conveying  into  another  vessel  the  grease  which 
is  run  off  in  the  commencement  of  the  operation;  K  another 
gutter,  moving  on  a  pivot,  which  receives  the  liquid  as  it  runs 
from  the  cock  g,  and  empties  it  into  the  tub  A,  or  into  the 
trench  i;  I  a  tube  for  feeding  the  interior  of  the  cylinder  with 
fresh  water;  m  a  movable  adjustment  attached  to  the  pipe  I 
for  regulating  the  quantity  of  water  and  preventing  a  too 
great  elevation  of  temperature  in  the  interior  of  the  appa- 
ratus. 

Fig.  260,  elevation  of  the  interior  basket,  made  of  wire- 
cloth.  This  basket,  or  cage,  receives  the  cleansed  and  crushed 
bones,  and  is  enclosed  in  the  cylinder  A;  a  is  the  handle  with 
which,  by  means  of  a  pulley,  it  is  lifted  or  lowered,  to  be 
emptied  or  charged.  Four  or  more  of  these  machines  make 
a  series,  and  the  boiler  which  feeds  them  with  steam  should 
carry  a  pressure  of  4  lbs.  to  the  inch.     [Encyc.  of  Ohem.) 

When  volatile  or  costly  liquids  are  used  as  solvents,  it  is 
necessary  both  on  the  score  of  economy  and  of  the  efficacy  of 
the  process  to  use  certain  precautions.  In  making  pharma- 
ceutical preparations,  of  which  alcohol  or  ether  is  the  men- 
struum, they  have  an  important  bearing.  For  example,  either 
of  these  liquids  volatilizes  by  a  high  heat,  and  unless  the 
vaporized  particles  are  by  a  suitable  arrangement  condensed 
and  returned  to  renew  action  upon  the  substance,  the  latter 
will  be  evaporated  to  dryness  long  before  sufficient  time  has 
elapsed  for  the  completion  of  its  solution.  For  this  purpose 
an  ordinary  cooling  worm  may  be  attached,  as  shown  in  Fig. 
261.  The  vapors  escaping  from  the  digesting  vessel  «,  are 
condensed  partly  in  the  inclined  tube  ?,  and  partly  in  the 
worm  c,  and  fall  back  again  into  the  flask  as  soon  as  they 
become  liquefied  by  the  water  surrounding  the  worm.     This 


306 


SOLUTION. — MOHR'S  DIGESTER. 


arrangement  allows  a  prolonged  contact  of  solids  witli  volatile 
liquids,  without  loss  or  alteration  of  the  latter — a  very  import- 
ant consideration,  as  time  is  an  influential  adjunct  in  diges- 
tion. 


Fig.  261. 


Fig.  262. 

a 


4 


!  T 


Mohr  improves  upon  the  above  apparatus,  by  substituting 
another,  exhibited  in  Fig.  262.  It  consists  of  a  tin  plate 
cylinder  A,  tubulated  at  its  bottom.     Through  this  tubulure 


SOLUTION. — BOILING  ;— IN  TUBES.  307 

passes  a  glass  tube  1 1,  adjusted  by  perforated  corks  to  the 
tubulures  of  both  cylinder  and  digesting  vessel  M.  The  va- 
porized matter,  ascending  from  the  heating  vessel  M,  is  cooled 
by  the  water  in  the  cylinder,  and  which  surrounds  the  tube  t  t. 
The  long  barreled,  tin  plate  funnel  T,  receives  the  amount  of 
water  freshly  added,  and  conveys  it  to  the  bottom  to  displace 
that  which  has  become  heated,  and  which  by  its  less  density 
rises  to  make  its  escape  through  the  outlet  A. 

Solution  by  Boiling.— This  mode  is  resorted  to  when  a 
substance  can  only  be  exhausted  of  its  soluble  portion  at  the 
boiling  point  of  the  solvent.  The  exact  point  of  temperature 
at  which  a  liquid  boils,  depends  partly  upon  the  amount  and 
fluctuations  of  pressure,  and  the  nature  and  construction  of 
the  vessel.  When  the  pressure  of  supernatant  vapor  is  re- 
moved by  uncovering  the  vessel,  ebullition  is  facilitated  and 
takes  place  at  lower  temperatures.  Indentation  or  roughen- 
ing of  the  surface  of  the  heating  vessel,  or  any  other  means 
by  which  the  heating  surface  is  increased  and  escape  of 
gaseous  matter  is  promoted,  lowers  the  boiling  point  of  a 
liquid.  For  this  latter  reason,  platinum  scraps  or  pieces  of 
unglazed  card,  or  of  cork,  pacify  turbulent  ebullition  and 
render  the  process  tranquil  and  uniform. 

The  heat  applied  should  never  exceed  the  degree  at  which 
the  solvent  boils,  especially  in  metallic  vessels,  otherwise  ebul- 
lition is  retarded,  for  beyond  a  certain  temperature  a  repul- 
sion between  the  particles  of  liquid — when  water  is  used — and 
the  metallic  surfaces,  prevents  contact. 

The  kind  of  apparatus  varies  with  the  nature  and  quantity 
of  material  under  process. 

Boiling  in  Tubes. — Test  tubes.  Fig.  263,  are  very  conve- 
nient implements  for  delicate  solutions,  assays  and  the  like, 
and,  therefore,  the  laboratory  should  be  supplied  with  a  large 
assortment,  varying  from  three  inches  in  length  and  a  quarter 
inch  in  diameter  to  six  inches  in  length  and  one  inch  in  dia- 
meter. They  should  be  of  hard,  white  German  glass,  free  from 
lead,  with  perfectly  round  bottoms,  uniformly  thin,  so  as  to 
withstand  heat.  The  racks,  Figs.  25  and  147,  serve  as  their 
supports. 

A  test  tube  should  never  be  charged  with  more  than  one- 
third  its  capacity  of  solvent,  else  there  may  be  loss  by  ejec- 
tion from  too  sudden  ebullition ;  and  the  solid  substance  pre- 


308 


SOLUTION  IN  TEST  TUBES. 


viously  powdered  is  not  to  be  added  until  the  liquid  is  brought 
to  boiling,  and  then  only  in  small  portions  at  a  time. 

To  guard  against  spirting  or  to  ensure  a  uniform  heating, 
the  tube  must  be  gradually  heated,  not  upon  its  bottom  but 
near  to  or  on  the  side,  as  shown  in  Fig.  264.  It  is,  as  seen, 
heated  over  the  small  lamp,  Fig.  115,  being  held  in  the  fin- 
gers, which  are  protected  from  contact  with  the  hot  glass 


Fig.  263. 


Fig.  264. 


yj 


by  a  doubled  strip  of  thick  paper  wrapped  around  the  neck 
of  the  tube  for  its  support.     The  spring  holder,  Fig.  265, 

Fig.  265. 


SOLUTION  IN  TEST  TUBES.  309 

consisting  of  a  wooden  handle  affixed  to  two  flat  pieces  of  thin 
steel  indented  at  their  ends  so  as  to  form  a  round  catch,  and 
tightened  or  loosened  bj  a  slide,  is  much  more  convenient  but 
not  always  at  hand. 

The  mouth  of  the  tube  during  heating,  or  whilst  its  contents 
are  being  shaken,  should  always  be  held  away  from  the  ope- 
rator, else  ejected  matter  may  endanger  his  person  or  dress. 

Faraday  gives  the  following  valuable  advice  as  to  the  use 
of  test  tubes  for  making  solutions  with  volatile  liquids,  and 
under  pressure. 

"  In  consequence  of  the  small  diameter,  and  therefore 
small  sectional  area  of  tubes,  they  are  much  stronger  rela- 
tively to  internal  pressure  than  larger  vessels,  such  as  flasks 
of  the  same  thickness.  An  advantage  is  thus  gained  in  some 
cases  of  solution  or  digestion  in  certain  fluids,  as  alcohol, 
ether,  and  even  water,  because  it  enables  the  experimenter  to 
subject  the  substances  to  temperatures  as  high  as  the  boiling 
points  without  loss  of  the  fluid,  or  occasionally  to  tempera- 
tures still  higher,  the  ebullition  going  on  as  it  were  under 
pressure.  This  is  easily  performed  with  alcohol,  ether,  and 
similarly  volatile  fluids,  in  tubes  of  four,  five,  or  six  inches 
in  length,  and  of  such  diameter  as  to  be  readily  and  per- 
fectly closed  by  the  finger.  Suppose  a  tube  of  this  kind,  one- 
third  filled  with  alcohol  and  held  tightly  between  the  thumb 
and  second  finger  of  the  right  hand,  its  orifice  being  closed  by 
the  fore-finger  of  the  same  hand.  Fig.  251.  The  fore-finger 
is  to  be  relaxed,  and  the  heat  of  a  spirit-lamp  applied  until 
the  alcohol  begins  to  boil ;  the  fore-finger  is  then  to  be  reap- 
plied closely,  and  it  will  be  found  that  the  flame  of  the  lamp, 
applied  at  intervals,  is  quite  sufficient  to  keep  the  temperature 
up  to  the  boiling  point.  No  alcohol  can  evaporate,  for  the 
finger  has  power  sufficient  to  retain  the  vapor  even  were  its 
force  equal  to  two  atmospheres,  and  the  tube  itself  is  also 
strong  enough  to  resist  the  same  force. 

*'  This  operation  is  very  advantageous  when  valuable  and 
volatile  solvents  are  in  use ;  it  is  therefore  worth  while  to  refer 
to  those  points  which  indicate  the  state  and  temperature  of 
the  fluid,  and  which  make  the  practice  easy.  If  the  fluid  be 
one  which,  like  alcohol,  when  at  or  above  its  boiling  point  is 
at  a  temperature  inconvenient  to  the  hand,  then,  if  all  the 
common  air  were  allowed  to  pass  out  of  the  tube  before  clos- 
ing it,  the  whole  tube  would  become  heated  by  the  vapor 


310  BOILING  IN  BEAKER  GLASSES  AND  FLASKS. 

rising  from  the  hot  liquid  beneath,  and  the  fingers  would  be 
injured ;  but  by  not  allowing  all  the  air  to  escape,  that  por- 
tion which  is  retained  in  the  tube,  is  always  forced  to  the  top 
by  the  successive  formation  and  condensation  of  the  vapor 
below,  and  interfering  with  the  passage  of  the  hot  vapor  to 
the  part  which  it  occupies,  it  preserves  that  portion  of  the 
tube  at  comparatively  low  and  very  bearable  temperatures. 
The  part  thus  retained  at  a  low  temperature,  is  proportionate 
to  the  quantity  of  air  confined  in  the  tube ;  this  quantity  is 
usually  a  proper  one  if  the  tube  be  closed  just  after  the  alco- 
hol has  begun  to  boil,  and  before  the  upper  part  of  the  tube 
has  been  heated.  If  too  much  air  has  been  expelled,  and 
the  tube  is  found  to  become  hot  above,  the  application  of  the 
flame  must  be  suspended  a  moment  or  two,  the  whole  sufiered 
to  cool  below  the  boiling  point,  the  tube  opened,  the  upper 
part  cooled  slightly  by  a  piece  of  moist  paper  or  a  cold 
finger,  and  then  the  fore-finger  is  to  be  reapplied  to  close  it 
as  before. 

"  The  state  of  the  fluid  within  is  in  part  indicated  by  the 
pressure  of  the  air  or  vapor  on  the  finger,  the  latter  being 
urged  away  from  the  tube  by  a  force  proportionate  to  the 
degree  of  heat  above  the  boiling  point,  and  being  drawn  in- 
wards when  the  heat  is  below  that  point.  Generally,  there- 
fore, the  finger  alone  will  serve  to  ascertain  whether  the 
temperature  is  above  or  below  the  point  of  ebullition;  but 
as  the  force  required  is,  after  operating  for  some  time  at  high 
pressures,  such  as  to  diminish  the  sensibility  of  the  finger  to 
smaller  pressures,  it  sometimes  happens  that  on  lowering  the 
temperature,  the  period  at  which  it  attains  that  of  ebullition 
in  the  atmosphere  cannot  be  distinguished.  This  point  is, 
however,  easily  recognized  by  relieving  the  pressure  of  the 
finger  slightly ;  should  the  quiescent  fluid  below  then  burst 
into  ebullition,  it  is  a  proof  that  its  temperature  is  higher 
than  the  boiling  point  at  atmospheric  pressure,  but  should  it 
remain  quiescent  until  the  finger  is  entirely  removed,  its  tem- 
perature will  be  known  to  be  below  that  point." 

Boiling  in  Beaker  Glasses  and  Flasks. — These  vessels  are 
used  when  large  quantities  of  liquid  are  to  be  operated  upon. 
When  the  direct  heat  of  the  lamp  is  applied,  it  should  be 
diffused  by  the  intervention  of  a  wire  gauze.  The  preferable 
mode  of  heating  is  by  a  highly  heated  sand-bath.  The  same 
remarks  as  to  their  material  and  construction,  as  given  before 


J 


BOILING  IN  CAPSULES. 


311 


at  p.  303,  are  applicable  in  this  instance.  They  should  be 
loosely  covered  during  the  operation,  the  beaker  glasses  with 
squares  of  window  glass  and  the  mouths  of  the  flasks  with 
watch  glasses.  The  position  of  the  beaker  glass  over  the  lamp 
is  shown  at  Fig.  255,  that  of  flasks  at  Fig.  119.  Round  bot- 
tomed flasks,  Figs.  266,  267,  are  made  of  different  sizes,  espe- 


Fig.  266. 


Fig.  267. 


Fig.  268. 


cially  for  solutions,  but  Florence  flasks,  which  have  been 
rounded  on  the  edges  of  the  mouth  over  the  blow-pipe  flame, 
so  as  to  allow  of  the  easy  entrance  of  a  loose  cork,  are  equally 
convenient  and  less  costly.  They  are  thin  and  uniform 
throughout,  and  bear  very  high  temperatures  without  frac- 
ture. Fig.  268  represents  a  flask  being  heated  in  a  dish 
sand-bath  over  a  small  furnace,  for  solutions  requiring  a  higher 
temperature  than  can  be  furnished  by  the  gas  or  spirit  lamp. 
They  must  be  well  imbedded  in  the  sand  in  order  to  produce 
ebullition. 

Boiling  in  Capsules. — Solution  is  made  in  open  vessels 
when  the  solvent  liquid  is  not  easily  vaporizable  or  alterable 
by  exposure,  or  when  its  loss  is  of  little  consequence.  The 
most  convenient  implements  for  the  purpose  are  porcelain 
capsules.     Figs.  269,  270.     Those  from  the  Royal,  Dresden 


Fig.  269. 


Fig.  270. 


312  SOLUTION  BY  STEAM. 

and  Berlin  factories  are  far  superior  to  the  French,  or  those 
of  anj  other  make.  They  are  strong  yet  uniformly  thin 
throughout,  and  support  very  high  temperatures  and  sudden 
changes.  Being  enamelled  they  are  protected  from  the  action 
of  acids  or  corrosive  liquids,  and  consequently  are  of  general 
application.  They  are  sold  of  all  sizes,  by  Kent,  varying  up- 
wards from  an  ounce  to  18  oz.  in  capacity.  The  diameter  of 
the  smallest  is  about  2  inches,  and  that  of  the  largest  15J 
inches.  The  depth  should  be  one-third  of  the  diameter.  The 
smaller  sizes  come  in  nests  of  a  half  dozen  or  more.  Fig. 
269  represents  one  with  spreading  rim  and  lip  to  facilitate 
pouring.  That  shown  in  Fig.  270  has  a  more  hemispherical 
shape. 

Capsules  are  almost  always  heated  over  the  open  fire,  the 
spirit  or  gas  lamp  furnishing  the  requisite  temperature.  Those 
of  smaller  size  are  shown  in  position  upon  suitable  supports  at 
Fig.  118,  and  2,  Fig.  119  ;  for  the  larger  Luhm^'s  lamp.  Fig. 
122  answers  an  admirable  purpose. 

The  liquid  is  placed  in  the  capsule  before  the  ignition  of 
the  wick,  and  when  it  is  boiling,  the  substance  to  be  acted  on 
should  be  gradually  deposited  in  it  in  a  finely  divided  state, 
while  constant  stirring  with  a  glass  rod  is  kept  up.  After  all 
has  been  added,  both  ebullition  and  stirring  must  be  con- 
tinued until  the  completion  of  the  process,  taking  care  to 
supply  the  loss  of  the  volatilized  portion  by  fresh  additions  of 
the  solvents,  unless  the  solution  is  to  be  evaporated. 

When  the  nature  of  the  materials  requires  the  intervention 
of  a  medium  other  than  sand  to  modify  the  heat,  a  rare  oc- 
currence when  operating  in  capsules,  the  latter  are  heated 
over  baths,  as  shown  at  Fig.  150.  Capsules  or  boiling  pans 
of  enamelled  iron  ware  or  tinned  copper  are  used  only  in  very 
large  operations. 

Solution  by  Steam. — "When  a  substance  is  to  be  dissolved 
by  steam  heat,  and  the  nature  of  the  materials  renders  the 
direct  application  of  steam  inadmissible,  then  baths.  Fig.  11, 
come  very  appropriately  into  play. 

For  aqueous  solutions  which  are  greatly  facilitated  by  the 
immediate  action  of  steam,  it  is  supplied  through  flexible  lead 
tubes  leading  from  the  generator.  Fig.  10,  directly  into  the 
containing  vessel. 

For  small  operations  in  glass  vessels,  the  copper  spritz, 


SOLUTION  BY  DISPLACEMENT.  313 

Fig.  186,  half  filled  with  water  and  heated  over  the  gas  lamp, 
readily  furnishes  sufficient  steam. 

As  boiling  by  steam  is  practiced  in  numerous  chemical  ope- 
rations, it  is  proper  to  introduce  some  directions  pertinent  to 
the  subject. 

It  is  very  seldom  that  the  heat  required  for  ordinary  labo- 
ratory purposes  exceeds  that  given  by  five  pounds  above 
atmospheric  pressure — never  more  than  fifteen  pounds — and 
the  fire  under  the  generator  and  weights  upon  the  safety 
valve  should  be  regulated  accordingly. 

If  the  mixture  to  be  boiled  is  unalterable  by  the  action  of 
condensed  steam,  the  conduit  pipe  may  lead  directly  into  it, 
and  to  the  bottom. 

As  the  liquid  appears  to  boil  before  it  actually  does,  the 
only  sure  indication  of  temperature  is  to  be  obtained  by  a 
thermometer.  Fig.  84. 

This  method,  however,  causes  a  great  loss  of  heat  and  in- 
commodes the  operator,  by  filling  the  apartment  with  clouds 
of  vapor.  A  loose  cover  will  partially  remove  these  objections. 
In  boiling  in  this  way,  care  must  be  taken  that  the  fire  does 
not  get  low,  lest  a  condensation  of  the  vapor  occupying  the 
upper  part  of  the  boiler  causes  a  partial  vacuum,  and  the  con- 
sequent withdrawal  of  part  of  the  liquid  from  the  vat  into  the 
boiler.  The  conduit  connected  with  the  feeder  should  always 
have  a  stop-cock  near  the  coupling,  which  is  to  be  shut  off 
upon  the  completion  of  the  operation.  If  the  boiler  should 
then  happen  to  be  surcharged  with  steam,  it  must  be  blown 
off  through  the  valve,  this  being  readily  accomplished  by 
gradually  unloading  the  lever. 

A  far  better  plan  of  boiling  by  steam  is  to  conduct  it 
through  a  coil  of  pipe  placed  at  the  bottom  of  the  vat,  and 
having  an  exhausting  pipe  leading  into  the  neighboring  flue. 
This  mode  allows  a  uniform  temperature  at  any  degree  from 
that  of  the  atmosphere  to  212^  F., — suitable  stop-cocks  being 
attached  for  that  purpose  to  regulate  the  supply  of  steam  ac- 
cordingly. 

In  cold  weather  and  especially  when  the  feeder  or  conduit 
are  of  any  length,  it  will  be  economical  to  wrap  them  with 
woolen  listings  or  straw,  as  means  of  preventing  conden- 
sation. 

Solution  by  Displacement. — Displacement,  termed  also 
lixiviation,  when  applied  to  the  solution  of  saline  substances, 
21 


314 


SOLUTION  BY  DISPLACEMENT. 


is  an  economical  process  for  the  extraction  of  the  soluble  por- 
tions of  woods,  leaves,  flowers,  barks,  precipitates,  and,  indeed, 
of  all  matters  to  which  suitable  apparatus  can  be  adapted  for 
the  infiltration  of  a  sufficiency  of  liquid  through  them.  For 
delicate  operations  and  those  conducted  upon  a  scale  of  mo- 
derate extent,  glass  vessels  may  be  employed.  One  of  the 
usual  form  is  shown  in  Fig.  271.  It  is  made  of  hard  glass, 
free  from  lead,  the  upper  part,  or  A,  being  the  displacer, 
and  the  lower  part,  B,  an  ordinary  flask,  the  recipient  of  the 

Fig.  271. 


saturated  solution.  The  mouth  of  the  bottle  and  that  portion 
of  the  displacer  which  rests  in  it  should  be  ground  so  as  to 
make  a  close  joint.  The  stopple  is  for  closing  the  upper  ves- 
sel when  necessary.  Dobereiner's  improvement  upon  the  above, 
but  operating  upon  the  same  principle,  is  shown  in  Fig.  272. 
To  prevent  the  passage  of  the  material  through  the  barrel  of 
the  displacer,  it  must  be  loosely  closed  with  a  plug  of  raw 
cotton  as  at  /,  and  then  adjusted  by  means  of  a  perforated 
cork  g,  with  the  vertical  tubulure  of  the  globular  receiver  a. 
The  whole  apparatus  as  adjusted  is  retained  in  an  upright 
position  by  a  support,  the  receiver  resting  upon  a  braided 
straw  ring.  It  is  now  ready  to  receive  its  charge.  The 
substance  in  coarse  powder  and  moistened,  occupies  the  part 
of  the  vessel  e,  and  the  solvent  is  subsequently  added  as  at  d. 
A  partial  vacuum  being  made  in  the  receiver  by  the  evapora- 


SOLUTION  BY  DISPLACEMENT.  315 

tion  of  a  few  drops  of  alcohol  added  through  the  lateral  stop- 
pered tubulure  c,  the  liquid  percolates  through  the  solid  mass 
by  the  force  of  atmospheric  pressure,  and  ultimately  reaches 
the  receiver  saturated  with  the  soluble  matter  of  the  mate- 
rial e. 

In  order  to  express  clearly  the  rationale  of  this  process,  we 
will  suppose  that  vegetable  matter,  a  dye-wood  for  example, 
in  coarse  powder,  is  to  undergo  exhaustion  by  this  method. 
It  occupies  the  part  e,  as  before  said,  and  to  facilitate  the  per- 
colation, has  been  previously  moistened  with  a  portion  of  the 
solvent.  Liquid  is  added,  as  shown  at  d,  and  soon  soaks  into 
the  mass  beneath ;  another  portion  of  solvent  is  then  poured 
in  as  before,  and  takes  the  same  course,  displacing  the  portion 
before  used  without  mixing  with  it.  These  strata  of  solvent 
are  pressed  downwards  by  successive  additions  of  liquid,  and 
become  more  and  more  charged  with  soluble  matter,  as  they 
approach  the  bottom  of  the  mass,  until  at  last  they  run  out 
into  the  recipient  highly  charged  and  in  the  present  instance, 
highly  colored — the  first  runnings  being  more  nearly  saturated 
than  those  which  follow.  When  by  consecutive  additions  of 
solvent  the  material  has  been  exhausted,  the  liquid  in  its 
transit  through  the  mass  is  unacted  upon,  and  reaches  the 
receiver  as  tasteless  and  uncolored  as  when  first  poured  in. 
This  indicates  the  completion  of  the  process. 

The  neck  of  a  retort  with  its  smaller  end  adjusted  to  a  wide 
mouth  bottle  by  means  of  a  perforated  cork,  makes  an  excel- 
lent displacing  apparatus. 

When  the  solvent  is  volatile,  in  order  to  prevent  loss  by 
evaporation,  the  apparatus  is  modified,  as  shown  in  Fig.  273. 
The  displacer  is  adapted  to  the  centre  tubulure 
of  a  two  necked  Wolffe  bottle.     Now  as  atmo-        Fig.  273. 
spheric  pressure  is  an  important  element  of  this 
process,  it  will  not  do  to  shut  it  ofi"  by  closing 
the  top  of  the  displacer  without  making  some 
other  arrangement,  and,  therefore,  a  communi- 
cation between  the  upper  and  lower  vessel  is 
established  by  means  of  a  bent  tube  adjusted 
in  the  lateral  tubulure  of  each.     In  this  man- 
ner the  vessel  is  completely  closed,  and  vapor- 
ization prevented  while  the  pressure  produced 
is  distributed  throughout  the  vessel,  and  thus 
rendered  uniform.     In  using  the  glass  displacement  appa- 


I 


316  SOLUTION  BY  DISPLACEMENT. 

ratus  first  described,  this  principle  must  be  recollected ; 
where  a  vacuum  is  not  artificially  created  in  the  receiver,  the 
ground  glass  edges  of  it  and  the  displacer  should  either  be 
permanently  separated  or  occasionally  disjointed. 

The  stop-cock  near  the  bottom  of  the  receiver  allows  the 
withdrawal  of  the  solution  as  fast  as  it  accumulates,  without 
the  necessity  of  disarranging  the  apparatus.  In  experiments 
upon  large  quantities  of  material,  and  in  pharmaceutical  ope- 
rations generally,  the  displacers  employed  are  made  of  tinned 
copper  or  tin  plate.  Those  of  porcelain  which  are  now  in  the 
market,  are  much  more  serviceable,  because  they  are  readily 
cleansed  and  resist  the  action  of  corrosive  liquids.  Of  what- 
ever material  they  are  made,  they  should  be  cylindrical  and 
funnel-shaped  at  the  base,  and  the  height  should  be  at  least 
four  times  the  diameter,  as  is  shown  in  Fig.  274.  At  a 
there  is  a  flange  in  the  interior  as  a  support  for  the  cul- 
lendered  diaphragm  a  h.  These  diaphragms  are  removable, 
and  for  convenience  in  handling  have  a  knob  in  the  centre. 
The  lower  diaphragm  is  always  to  be  covered  with  a  circle 
of  coarse  muslin  for  the  reception  of  the  material  and  to  pre- 
vent the  passage  of  particles  as  well  as  obstruction  of  the 
holes.  The  other  diaphragm,  fitting  loosely  to  the  cylinder, 
rests  upon  the  top  of  the  powder  and  serves  for  the  better 
distribution  of  the  solvent  and  for  the  prevention  of  the  escape 
of  dusty  particles  which  sometimes  occurs  if  the  powder  is  put 
in  dry.  The  stop-cock  c  in  the  barrel  or  exit  pipe  is  useful 
for  regulating  the  discharge  of  the  liquid. 

The  tripod  D  is  the  support,  and  allows  the  withdrawal  of 
the  receiver  P,  when  it  is  full  and  when  it  is  to  be  replaced 
by  another,  without  the  necessity  of  disturbing  the  displacer. 

Another  very  convenient  form  of  displacer  is  that  in  which 
ether,  alcohol  and  any  other  volatile  solvent  may  be  kept  in 
constant  action  without  exposure  to  air  or  loss  by  evaporation. 
By  its  use  a  great  saving  of  time  and  labor  and  solvent  is 
gained.  The  arrangement  is  exhibited  at  Fig.  275.  It  con- 
sists of  a  glass  cylinder  B,  the  funnel  of  which  should  reach 
to  the  centre  of  a  glass  balloon  A,  beneath  the  two  vessels, 
being  attached  by  means  of  a  perforated  cork.  The  lateral 
tube  c,  d  opens  communication  between  the  lower  and  upper 
apartments.  As  the  whole  forms  a  perfectly  tight  connection, 
the  safety  tube  E  becomes  necessary  for  the  regulation  of  the 
dilatation  and  contraction  of  the  vapors. 


SOLUTION  BY  DISPLACEMENT. 


317 


When  it  is  desired  to  exhaust  a  vegetable  matter  with 
alcohol  or  ether,  and  at  one  and  the  same  operation  to  con- 


Fig.  274. 


Fig.  275. 


C      'HllfiDi 


centrate  the  charged  solvent,  plug  the  barrel  of  B,  with  raw 
cotton,  previously  moistened  with  the  liquid  to  be  used,  add 
the  powdered  material,  cover  it  with  a  cullendered  disc,  pour 
on  the  liquid  in  quantity  sufficient  to  give  a  filtered  solution 
of  half  the  capacity  of  the  balloon,  and  then  connect  the 
apparatus.  The  balloon  is  now  to  be  placed  half  its  depth  in 
the  water  bath  H,  and  the  apparatus  sustained  in  a  perpen- 
dicular position  by  means  of  a  clamp  support.  The  water 
bath  is  to  be  closed  with  a  loose  cover,  and  heated  as  may  be 


318  SOLUTION  IN  CLOSE  VESSELS. 

required  by  the  small  spirit  lamp  i.  The  ether  or  alcohol 
which  has  infiltrated  into  the  balloon  thus  carried  to,  and 
maintained  at  ebullition,  passes  oflf  as  vapor  into  the  lateral 
tube,  there  partially  condenses  and  falls  upon  the  material  in 
the  cylinder  to  infiltrate  through  again.  The  excess  of  vapor 
and  of  expanded  air  escapes  through  the  safety  tube ;  but  a 
part  of  the  vapor  is  arrested  and  condenses  in  the  three  bulbs, 
the  first  of  which  immediately  empties  its  liquefied  contents 
into  the  cylinder  to  renew  its  action  upon  the  powder. 

The  concentration  of  the  filtered  solution  is  thus  continually 
going  on  in  the  balloon,  the  concurrent  distillation  returning 
the  evaporated  particles  to  the  substances  to  be  exhausted, 
through  the  lateral  tilbe  c,  d. 

When  water  is  the  liquid  to  be  employed,  the  water  bath 
must  be  replaced  by  a  saline  or  sand  bath,  and  the  spirit  lamp 
by  a  furnace. 

For  the  solution  of  diflScultly  soluble  substances,  this  mode 
presents  many  advantages  not  possessed  by  other  processes, 
and  amongst  others  it  yields  a  clear  solution  and  supersedes 
the  necessity  of  filtration,  which  is  required  for  most  solu- 
tions made  by  infusion,  decoction  and  boiling.  It  is  par- 
ticularly applicable  to  the  purpose  of  procuring  concentrated 
solutions  for  evaporation  to  extracts,  as  well  as  for  making 
tinctures,  &c. 

The  solvent  may  be  acid,  alkaline,  spirituous,  ethereal  or 
aqueous  in  its  nature,  the  principle  of  its  action  being  the 
same  in  all  cases.  When  the  liquid  is  corrosive,  however,  the 
vessel  should  not  be  metallic,  but  of  glass  or  porcelain,  and 
should  be  plugged  with  asbestos  instead  of  cotton.  It  is  im- 
material whether  the  solvent  be  applied  cold  or  warm,  save 
when  the  process  is  resorted  to  for  the  separation  of  sub- 
stances soluble  in  cold  from  those  which  are  only  soluble  in 
hot  liquids.  Except  in  such  cases  heat  may  be  applied,  as  it 
increases  the  power  of  the  solvent,  and  a  convenient  means 
of  doing  so  is  to  encompass  the  apparatus  with  a  metallic 
jacket,  to  be  supplied  with  steam  from  the  generator.  Fig.  10. 

There  are  certain  conditions  necessary  to  the  success  of 
this  operation.  The  material  must  be  in  powder  of  medium 
division;  neither  too  fine  nor  too  coarse,  for  in  the  first 
case  it  clogs  the  cloth  and  holes  of  the  diaphragm,  and  if 
heavy  and  compact,  retards  the  percolation  of  the  liquids: — 
on  the  other  hand,  when  too  gross,  the  transit  of  the  solvent  is 


cadet's  mode  of  solution.  319 

so  rapid  that  the  material  is  but  partially  acted  upon.  When 
alcohol  or  ether  is  used,  the  powder  may  be  a  little  finer  than 
for  less  volatile  solvents;  and  all  powders  liable  to  set,  or  to 
become  so  compact  as  to  prevent  the  passage  of  liquid,  must 
previously  be  mixed  with  well  washed  coarse  white  sand.  This 
addition  remedies  the  defect  and  ensures  the  easy  passage  of 
the  solvent. 

The  material,  as  before  recommended,  should  be  moistened 
with  half  its  weight  of  the  solvent,  and  left  to  soak  for  an 
hour  or  more  before  being  placed  in  the  percolator.  After 
having  been  transferred,  it  is  covered  with  the  diaphragm, 
and  sufficient  liquid  is  poured  upon  it  to  cover  entirely  its 
surface.  As  soon  as  this  first  portion  infiltrates  through  the 
mass,  another  portion  is  added,  for  it  is  only  by  keeping  the 
surface  covered  with  solvent  that  a  uniform  penetration  of  all 
portions  of  the  mass  can  be  efiected.  If  the  liquid  passes 
through  very  rapidly  the  mass  is  too  loose,  and  must  therefore 
be  compressed  by  pressing  upon  the  diaphragm  cover.  Or  in 
order  to  prolong  their  contact,  the  stop-cock  c  may  be  nearly 
closed,  so  as  to  allow  the  exit  of  only  a  thin  stream. 

When  alcohol  or  other  valuable  volatile  liquid  is  used,  the 
residual  portions  may  be  either  extracted  by  pressure  of  the 
mass  p,  or  by  displacement  with  water;  and  subsequently,  by 
distillation  of  the  resulting  mixture.  The  general  practice, 
however,  in  the  Laboratory  is  to  reserve  the  last  running  for 
the  first  application  to  fresh  material. 

Cadet's  Mode  op  Solution — This  plan  is  well  adapted  to 
those  powders  which  do  not  admit  of  being  easily  infiltrated. 
It  consists  in  macerating  or  infusing  the  pulverized  material 
with  double  its  weight  of  cold  or  hot  solvent,  and  after  some 
time  subjecting  it  to  strong  pressure.  This  treatment  is  to 
be  repeated  until  the  substance  ceases  to  yield  soluble  matter, 
and  the  resulting  liquids  are  then  mixed  together  and  filtered. 
Cadet's  mode  is  used  largely  for  dissolving  the  tannin  from 
galls  with  ether. 

A  convenient  press  for  this  purpose  is  shown  at  Figs.  276 
and  277.  All  powders  which  have  undergone  the  process  of 
solution  in  large  quantity  should  be  subjected  to  its  action,  as 
a  good  deal  of  retained  solution  may  thus  be  obtained,  and 
consequently  saved. 

It  is  formed  of  two  strong  upright  stanchions,  and  two 
proportionably  strong  cross  pieces,  firmly  jointed  in  the  side 


320 


CADET  S  MODE  OF  SOLUTION. 


beams.  The  upper  cross  piece  carries  a  box  through  which 
works  an  ordinary  press  screw,  in  the  usual  manner.  Upon 
the  lower  cross  piece,  is  placed  a  wooden  trough,  A  (Fig.  277) 


Fig.  276. 


Fig.  277. 


n  I  n 


■ 


A 


at  least  two  inches  deep,  and  to  the  front  of  which  is  adapted 
a  gutter  B  for  the  conveyance  of  the  liquid,  which  assembles 
in  the  trough,  to  a  vessel  E  placed  at  and  beneath  its  mouth. 
Upon  and  within  the  trough  is  placed  a  wrought  iron  plate 
cylinder.  This  cylinder  is  formed  of  two  semi-cylinders 
joined  together.  Throughout  its  height,  it  is  divided  off 
alternately  into  equal  parts  by  zones  or  belts.  The  zones  a  a 
are  more  than  an  inch  broad; — the  partition,  5,  &c.,  four  or  five 
inches  in  width.  The  top  as  well  as  the  lower  zone  is  narrow. 
All  the  wider  divisions  are  cullendered  throughout  their  cir- 
cumference with  innumerable  small  holes,  through  which  the 
liquid  is  to  flow  when  pressure  is  applied.  All  the  narrow 
zones  are  secured  by  a  strong  wrought  iron  ring,  formed 
of  two  pieces  working  on  a  hinge  adjusted  at  the  back.  Upon 
the  front  is  a  movable  broach  D,  which  bolts  them  together, 
and  makes  the  cylinder  compact,  so  that  it  can  resist  the 
pressure  applied.  When  the  marc  is  exhausted,  by  draining 
out  the  broach  D,  the  circumference  of  the  cylinder  is  loosened 
or  extended,  so  that  its  contents  can  be  removed  without 
difficulty.  The  marc  is  placed  in  this  cylinder  and  pressed 
out  by  the  power  of  the  screw,  until  no  more  fluid  will  exude, 
even  with  the  force  of  a  man  to  the  lever.  The  liquid  runs 
into  the  gutter  B  and  through  a  sieve,  which  should  be  pro- 
perly placed  for  the  purpose,  into  the  vessel  E,  and  may  thence 
be  drawn  off  after  it  has  settled,  into  suitable  vessels.     The 


SOLUTION  UNDER  PRESSURE  OF  STEAM. 


321 


residual  exhausted  powder  is,  as  said  above,  easily  emptied 
out  by  loosening  and  removing  the  pin  D. 

Solution  under  Pressure  of  Steam. — Figs.  278  and  279 
exhibit  Duvoir's  bucking  apparatus,  which  as  modified  in  the 


Fig.  278. 


Fig.  279. 


drawings,  is  applicable  to  the  exhaustion  of  organic  matter. 
B  B  are  the  wooden  vats  lined  with  lead  which  receive  the 
material  to  be  displaced ;  a  G  the  cullendered  diaphragms  for 
its  support;  and  c  c  their  movable  covers  counterpoised  so  as 
to  admit  of  ready  depression  or  elevation  at  will.  These  false 
bottoms  are  also  movable,  so  as  to  afford  facility  in  cleansing 
the  vat,  and  they  should,  when  in  use,  be  covered  with  crash 
cloths  to  prevent  obstruction  of  the  holes.  The  tubes  d  d, 
communicating  with  the  steam  generator.  Fig.  10,  traverse 
the  centre  of  the  vats,  and  are  surmounted  by  metallic  discs, 
E  E,  for  the  reverberation  of  the  vapor  rushing  against  them. 
The  directions  for  the  management  of  the  apparatus  are 
nearly  the  same  as  for  displacement  generally.  When  the  vat 
has  received  its  charge,  the  cover  is  to  be  lowered  and  fastened 
down  by  clamps,  and  steam  let  on  by  opening  the  stop-cock 
of  the  feeder.  As  the  steam  generates,  it  passes  over  through 
the  pipe  D,  reaches  the  disc  E,  and  is  projected  uniformly  over 
the  whole  surface  of  the  material.  The  elastic  force  of  the 
vapor  accumulating  in  the  upper  portion  of  the  vat  exerts  a 
pressure  upon  that  portion  which  has  condensed  and  forces  it 
downwards  through  the  mass.     In  its  passage  it  becomes 


322.  EVAPORATION. 

charged  with  soluble  matter  and  reaches  the  lower  part  of  the 
vat  K  beneath  the  diaphragm,  whence  it  is  drawn  off  through 
the  cock  L,  R. 

As  a  safeguard  against  accidents  there  should  be  a  safety- 
valve  upon  the  cover  of  the  vat  as  well  as  upon  the  generator. 

This  arrangement  would  be  particularly  economical  in  the 
arts,  for  extracting 'dye  woods  and  other  vegetable  substances. 


CHAPTER   XXI. 

EVAPORATION. 

When  any  liquid  is  heated  for  the  purpose  of  expelling 
vaporizable  matter,  and  the  process  is  conducted  solely  with 
a  view  to  saving  its  fixed  portion,  the  operation  is  termed 
evaporation.  It  thus  far  differs  from  distillation,  which  has 
for  its  object  the  preservation  of  the  volatilized  portion,  in 
most  cases,  regardless  of  the  solid.  By  its  aid  we  can  decrease 
the  volume  of,  or  concentrate  solutions  for  crystallization  and 
chemical  reaction,  expel  valueless  volatile  ingredients  from 
those  which  are  more  fixed,  obtain  dissolved  matter  in  a  dry 
state,  and  prepare  extracts  and  other  pharmaceutical  pro- 
ducts. 

Liquids  evaporate  more  or  less  at  all  temperatures,  those 
having  the  lowest  boiling  point  yielding  the  most  readily ;  but 
there  are  certain  conditions  which  greatly  promote  this  tend- 
ency.    It  must  be  remembered,  therefore: — 

1.  That  evaporation  is  more  rapid  in  dry  atmospheres,  and 
that  consequently  the  transit  of  a  constant  stream  of  air  over 
the  surface  of  the  heated  liquid  effects  a  continual  removal 
of  each  stratum  as  it  becomes  saturated  with  vapor. 

2.  That  evaporation  is  confined  to  the  surface,  and  conse- 
quently that  the  breadth  of  the  evaporating  vessel  must  be 
extended  at  the  expense  of  its  depth. 

3.  That  heat  greatly  facilitates  evaporation  by  lessening 
the  cohesive  force  of  the  particles  of  a  liquid,  and  consequently 
that  the  evaporating  vessel  should  present  a  broad  surface  to 
be  heated. 


EVAPORATING  VESSELS. — SPONTANEOUS  EVAPORATION.    323 

4.  That  a  diminution  of  the  atmospheric  pressure  also 
facilitates  evaporation,  for  the  more  perfect  the  vacuum  the 
lower  the  boiling  point  of  a  liquid. 

Evaporating  Vessels. — For  analytic  purposes,  capsules  of 
Berlin  porcelain  are  by  far  the  best  implements.  The  cap- 
sules should  be  very  thin,  with  steep  sides,  spout  for  pour- 
ing, nearly  flat  bottomed,  and  glazed  throughout.  Watch 
glasses  answer  for  small  experiments,  but  require  to  be  very 
cautiously  heated,  as  they  are  readily  fractured. 

Beaker  glasses  are  also  used  for  evaporating  solutions  which 
would  lose  by  being  transferred.  Broad  mouthed  glass  flasks 
are  of  but  limited  application  for  evaporating,  and  are  only 
employed  for  slow  processes  with  valuable  liquids,  which  are 
liable  to  alteration  by  too  much  exposure  when  ebullition  is 
necessary. 

For  the  larger  operations  of  the  ^^s-  280. 

Chemist  or  Pharmaceutist,  vessels 
(Fig.  280)  of  copper,  tin,  enamelled 
iron,  tinned  copper,  and  for  some 
purposes  very  large  porcelain  cap- 
sules are  more  suitable. 

Retorts  are  used  when  the  vapor- 
ized particles  are  of  sufiicient  value 
to  be  condensed,  as  in  the  process  of  distillation. 

Spontaneous  Evaporation. — Those  liquids  which  are  very 
volatile,  or  which  become  altered  by  heat,  are  evaporated  by 
mere  exposure  to  the  atmosphere  at  its  ordinary  temperature. 
To  this  end  they  are  poured  into  broad  shallow  vessels,  and 
placed  aside  until  the  dissipation  of  all  vaporizable  matters, 
or  until  crystallization;  this  mode  of  evaporation  being  also 
employed  for  procuring  large  crystals,  which  are  better  de- 
fined than  those  obtained  by  rapid  evaporation. 

The  more  dry  and  hot  the  atmosphere  the  more  rapid  is 
the  evaporation.  In  order  to  maintain  a  continued  contact 
of  the  surface  of  the  liquid  with  strata  of  fresh  air,  the  vessel 
containing  it  should  be  placed  in  a  draught,  so  that  those 
portions  of  air  which  become  saturated  with  vapor  may  be 
displaced. 

When  the  air  might  act  injuriously,  and  a  vacuum  is  un- 
necessary, a  substance  may  be  evaporated  in  another  atmo- 
sphere, for  instance,  of  hydrogen  or  carbonic  acid.  For  this 
purpose  it  is  only  necessary  to  adjust  the  disengagement  leg 


324  EVAPORATION  IN  VACUO. 

of  the  apparatus  (Fig.  219)  to  the  tubulure  of  a  retort,  so  that 
its  end  may  reach  nearly  to  the  level  of  the  liquid  in  the 
latter.  The  generated  hydrogen  passes  into  the  retort  heated 
to  the  required  temperature,  and  promotes  the  discharge  of 
the  vapors  into  a  recipient  attached  to  the  beak  of  the  retort, 
and  fitted  with  a  small  tube  in  its  other  tubulure  for  the  dis- 
engagement of  uncondensed  portions. 

For  the  evaporation  of  solutions  of  sulpho-bases,  of  sulpho- 
salts,  and  of  all  substances  readily  oxidizable  by  exposure, 
this  process  is  better  applicable  than  that  with  the  air-pump, 
which  is  apt  to  be  attacked  when  the  eliminated  vapors  are 
corrosive. 

This  process  is  much  used  in  crystallization,  for  concen- 
trating alterable  solutions,  and  drying  precipitates. 

Evaporation  in  Vacuo. — We  have  already  referred  to  the 
happy  influence  of  diminished  atmospheric  pressure  in  facili- 
tating evaporation,  and  shall  now  speak  of  the  means  by 
which  it  is  accomplished,  and  the  particular  instances  in  which 
it  is  employed. 

This  mode  is  resorted  to  for  hastening  the  evaporation  of 
all  liquids,  but  more  especially  of  those  which  are  alterable 
by  exposure. 

In  small  experiments  we  use  a  capped  bell  glass  (pp.  337, 338) 
as  the  confining  space.  Under  this  bell  glass  is  placed  the 
broad  shallow  capsule,  with  its  liquid  contents,  supported  upon 
a  wire  tripod  resting  in  a  leaden  tray  containing  sulphuric 
acid,  dried  chloride  of  calcium,  fused  potassa,  or  some  other 
absorbent  material.  The  bottom  or  bed  of  the  bell  may  be  a 
ground  glass  plate,  and  to  seal  the  joints  hermetically  the  rim 
of  the  bell  should  be  greased.  Connection  being  made  by 
means  of  a  suitable  pipe  and  the  stop-cocks  between  the  bell 
and  the  syringe,  communication  is  opened  and  the  vessel 
exhausted  of  air.  The  pressure  being  thus  removed,  evapora- 
tion proceeds  rapidly,  and  until  the  absorbent  matter  becomes 
saturated  with  vaporized  particles,  or  the  bell  filled,  there  is 
no  impediment.  The  latter  can  be  partially  removed  by 
working  the  pump  at  frequent  intervals. 

When  an  air-pump  is  used  the  procedure  is  the  same,  but 
in  either  case  the  vacuum  must  be  produced  gradually,  other- 
wise the  sudden  ebullition  of  the  liquid  may  cause  ejection  of 
its  particles.  The  better  way  is  to  cease  pumping  as  soon  as 
the  barometer  attached  to  the  machine  indicates  from  two  to 


EVAPORATION  BY  HEAT  IN  OPEN  AIR.  325 

two  and  a  half  inches  pressure,  and  to  resume  the  process  of 
exhausting  again  at  intervals  of  fifteen  or  thirty  minutes. 

Other  modes  of  evaporating  in  vacuo,  as  practiced  in  the 
arts,  are  fully  described  in  lire's  Dictionary  of  Arts,  and 
under  Sugar  ^  in  the  '^  Encyclopedia  of  Chemistry  J"  Howard's 
and  Barry's  vacuum  pans  are  the  most  effective  implements. 
The  latter  is  applicable  in  Pharmacy  for  making  extracts  upon 
an  extensive  scale.  It  consists  of  a  hemispherical  pan  with 
a  tightly  fitting  cover,  in  the  centre  of  which  is  a  bent  tube 
leading  into  a  copper  spheroid  of  four  times  the  capacity  of 
the  pan.  This  tube  is  fitted  with  a  stop-cock,  which  allows  a 
communication,  at  will,  between  the  spheroid  and  pan.  An- 
other cock  at  the  opposite  end  is  made  so  as  to  couple  with 
the  conduit  of  the  steam  generator* 

The  liquid  to  be  evaporated  is  introduced  into  the  basin, 
which  is  then  to  be  hermetically  closed  and  placed  in  a  water 
bath.  The  cock  connecting  with  the  spheroid  being  closed, 
a  current  of  steam  is  let  on,  and  continued  until  the  entire 
expulsion  of  air  from  the  pan ;  access  of  steam  is  then  stopped 
by  closing  the  cocks,  and  a  sheet  of  cold  water  applied  to  the 
exterior.  A  condensation  of  vapor  ensues,  and  a  partial 
vacuum  is  produced.  Communication  being  then  opened  with 
the  caldron,  uniform  expansion  of  the  air  ensues;  and  as  the 
capacity  of  the  spheroid  is  four  times  greater  than  that  of  the 
pan,  the  latter  contains  only  one-fifth  of  its  original  amount 
of  air.  Several  repetitions  of  this  manipulation  produce  a 
sufficient  vacuum.  The  water  bath  is  then  heated  until  the 
liquid  within  the  pan  commences  to  boil,  as  may  be  seen 
through  the  small  window  left  for  the  purpose,  and  the  cool- 
ing of  the  spheroid  continued.  When  the  liquid  has  reached 
the  required  thickness,  the  operation  may  be  discontinued. 
In  this  way  ebullition  proceeds  at  100°  F.  under  a  pressure 
sixteen  times  less  than  that  of  air.  With  an  air  syringe 
attached  for  removing  the  vapor  as  fast  as  formed,  the  power 
of  the  apparatus  would  be  greatly  increased. 

Evaporation  hy  Heat  in  Open  Air. — Having  already  noted 
the  effects  of  heat  in  facilitating  evaporation,  we  proceed  to 
make  known  its  modes  of  application.  As  the  boiling  points 
of  solutions  differ,  so  accordingly  their  evaporations  are 
eff^ected  at  varying  temperatures.  For  example,  aqueous  or 
other  solutions  of  unalterable  matter  may  be  evaporated  over 
the  fire;  others  which  are  destructible  by  heat  require  the 


326 

intervention  of  Baths.  In  whatever  mode  the  operation  is 
performed  the  general  principles  are  the  same,  and  whether 
the  vessel  be  a  porcelain  capsule  or  metallic  pan,  the  greater 
its  width  in  proportion  to  its  depth  the  more  rapid  is  the 
evaporation.  Constant  agitation  with  a  stirrer  is  also  pro- 
motive of  the  process. 

Evaporation  over  Water  and  Saline  Baths. — When  solu- 
tions are  alterable  at  a  temperature  above  212°  F.,  the  cap- 
sule or  containing  vessel  is  heated  over  the  water-bath.  Fig. 
150. 

If  it  requires  a  higher  heat,  but  one  not  exceeding  300°  F., 
then  the  water  must  be  replaced  by  a  saline-bath,  p.  184. 

Evaporation  hy  Steam. — This  mode  has  many  advantages 
over  all  others,  not  among  the  least  of  which  is  that  with  the 
aid  of  the  generator,  Fig.  10,  any  number  of  vessels  may  be 
heated  simultaneously,  and  in  any  part  of  the  laboratory,  it 
being  only  necessary  to  have  conduits  of  sufficient  length  to 
convey  the  steam  to  them.  Moreover,  convenient  stop-cocks 
allow  a  regulation  of  the  heat,  and  consequently  all  danger 
of  injury  to  the  evaporating  solution  is  avoided.  By  increas- 
ing the  pressure  of  the  steam  the  temperature  of  the  solution 
is  also  elevated. 

Steam  is  applied  through  metallic  coils  placed  at  the  bot- 
tom of  the  containing  vessels,  and  having  an  exit  pipe  leading 
into  the  neighboring  flue,  or  else  by  means  of  metallic  casings. 
This  latter  mode,  by  far  the  best,  is  given  in  detail  at  pp.  42 
and  181. 

Evaporation  over  Sand-baths. — This  mode  is  much  used  in 
analyses  and  for  careful  evaporations,  requiring  temperatures 
greater  than  212°,  and  yet  not  so  high  as  those  given  by  the 
naked  fire.  The  position  and  arrangement  of  the  vessels  are 
as  directed  under  the  head  of  Sand-baths. 

Evaporation  hy  Heated  Air. — This  mode  is  admirably 
adapted  for  the  inspissation  of  the  natural  juices  of  plants  or 
for  preparing  dry  extracts.  It  is  also  applicable  to  the  com- 
pletion of  evaporations  which  have  been  carried  as  far  as  is 
safe  over  the  naked  fire.  Porcelain  plates  or  panes  of  win- 
dow glass  are  the  vessels  used,  and  a  stove  or  apartment  for 
their  reception  heated  from  95  to  110°,  with  a  free  draught 
passing  through  are  the  means  of  obtaining  the  required  tem- 
perature. The  juice  evaporates  either  to  thin  scales  or  else 
to  a  spongy  mass,  as  in  the  case  of  tannin  extracted  by  ether, 


EVAPORATION  BY  HEATED  AIR  ; — OVER  THE  FIRE.       32T 

and  as  soon  as  it  reaches  dryness,  the  plates  or  panes  are  to 
be  withdrawn,  and  their  contents  removed  with  a  spatula. 

Evaporation  over  the  Naked  Fire. — The  tendency  of  many 
substances  to  decomposition  over  fire,  especially  organic,  even 
when  in  solution,  renders  this  mode  inapplicable  save  when 
the  solvent  and  substance  dissolved  are  both  inalterable  below 
the  boiling  point  of  the  former.  It  is  resorted  to  for  expe- 
diting evaporations,  but  otherwise  is  far  more  inconvenient 
than  steam,  because  of  its  affording  less  facility  for  the  regu- 
lation of  the  heat  and  requiring  greater  attention.  The  con- 
taining vessel  should  be  placed  over  a  furnace  of  small  dimen- 
sions, and  its  contents  continually  stirred  with  a  porcelain 
spatula — this  precaution  preventing  decomposition  or  carboni- 
zation, provided  the  temperature  is  not  allowed  to  exceed  the 
boiling  point  of  the  solvent. 

In  analysis  and  other  processes,  the  heating  implement  is 
generally  the  gas  or  spirit  lamp.  Figs.  26,  27.  The  cap- 
sule filled  to  about  two-thirds  its  depth  with  liquid,  being 
placed  in  position,  the  flame  is  applied  gradually  and  main- 
tained just  low  enough  to  prevent  ebullition ;  and  in  order  to 
facilitate  the  process,  and  at  the  same  time  to  allay  turbulence, 
it  should  be  frequently  stirred  with  a  glass  rod.  The  same 
directions  apply  when  the  operation  is  performed  in  a  beaker 
glass,  as  is  done  in  some  analytic  experiments ;  and  Eig.  255 
shows  its  position  over  the  lamp. 

A  cover  of  white  paper  prevents  access  of  dust  without 
retarding  the  process,  but  care  must  be  taken  that  the  con- 
tents of  the  vessel  be  not  ejected  against  it,  thus  causing  a 
loss. 

In  evaporating  to  dryness,  towards  the  end  of  the  process 
the  flame  must  be  so  managed  as  to  impart  a  uniform  heat 
to  all  parts  of  the  thickened  solution.  The  interposition  of 
a  very  thin  plate  of  sheet  iron  between  the  flame  of  the  lamp 
and  the  bottom  of  the  heating  vessel  is  an  additional  means 
of  preventing  spirting.  These  precautions  and  constant  stir- 
ring will  prevent  the  loss  of  particles  which  is  liable  to  occur 
upon  the  disengagement  of  the  last  portions  of  liquid.  If  the 
liquid  drops  a  powder  during  the  operation,  the  vessel  must  be 
inclined,  and  in  order  to  prevent  spirting,  heated  above  the 
deposit. 

A  platinum  spatula  is  a  very  useful  implement  for  detach- 
ing any  efflorescent  matter  which  may  "travel  up"  the  sides 
of  the  vessel. 


328   CRYSTALLIZATION  ; — BY  FUSION  ; — BY  SUBLIMATION. 


CHAPTER  XXII. 

CRYSTALLIZATION. 

When  a  body  in  the  act  of  passing  from  a  liquid  or  gaseous 
to  a  solid  state  arranges  itself  in  symmetrical  forms,  the  pro- 
cess is  termed  crystallization,  and  the  parts  of  the  body  so 
aggregated  are  called  crystals. 

By  this  process  we  can  separate  crystallizable  from  amor- 
phous substances  dissolved  in  the  same  menstrua;  purify 
crystals  from  foreign  and  coloring  matters,  and  in  qualitative 
examinations,  be  enabled  to  determine  the  composition  of 
bodies  by  a  reference  to  the  characteristics  of  figure. 

The  modes  of  crystallization  are  by  fusion,  sublimation, 
SOLUTION  and  chemical  reaction. 

Crystallization  hy  Fusion. — Sulphur,  lead,  bismuth,  tin, 
antimony,  silver,  numerous  alloys,  anhydrous  salts  and  other 
fusible  substances  which  are  unalterable  by  heat  are  crystal- 
lizable by  FUSION. 

To  this  end  they  are  melted  at  the  lowest  possible  tempe- 
rature, and  allowed  to  cool  very  gradually.  As  soon  as  a 
crust  forms  upon  the  top,  which  may  be  readily  seen  by  the 
surface  becoming  furrowed,  it  must  be  pierced  with  a  rod  and 
the  still  fluid  portion  decanted  with  sufficient  dexterity  to 
prevent  it  from  cooling  during  the  process,  and  at  the  same 
time  from  injuring  the  crystals  coating  the  interior  of  the 
vessel. 

The  liquid  matter  should  be  placed  so  as  to  be  free  from  all 
vibration.  The  greater  the  mass  of  the  material  and  the 
more  slowly  it  is  cooled  the  more  voluminous  and  better  de- 
fined will  be  the  crystallization. 

Crystallization  by  Sublimation. — Volatile  solids,  as  iodine, 
camphor,  several  metallic  chlorides  and  mercurial  compounds, 
arsenic,  benzoic  acid,  iodide  of  lead,  &c.,  when  heated  as 
directed  in  sublimation,  yield  vapors  which,  in  cooling, 
take  the  form  of  crystals. 

Crystallization  from  Solution. — When  it  is  desired  to  ob- 


CRYSTALLIZATION  FROM  SOLUTION.  329 

tain  a  substance  in  crystals,  it  must  first  be  liquefied  or  made 
into  a  SOLUTION  with  an  appropriate  liquid.  If,  after  mak- 
ing the  solution,  there  be  any  insoluble  residue  it  must  be 
separated  by  filtration  ;  and  subsequently,  if  the  solution 
is  capable  of  decolorization  by  such  means,  it  should  be  boiled 
with  a  small  portion  of  clean  bone  or  ivory  black,  and  again 
filtered.  As  it  is  the  almost  universal  law  that  heat  increases 
the  solvent  power  of  bodies,  the  solution  should  generally  be 
made  and  clarified  at  the  boiling  point,  so  that  the  excess 
of  matter  taken  up  at  the  high  temperature  may  separate  on 
cooling  in  the  form  of  crystals. 

So  long  as  a  solution  is  dilute  it  yields  no  crystals ; — these 
latter  are  only  formed  when  the  containing  liquid  is  super- 
saturated, or,  in  other  words,  holds  more  than  it  can  retain; 
and  consequently  in  diminishing  the  quantity  of  the  liquid  by 
evaporation,  we  increase  the  density  of  that  which  re- 
mains, and  hence,  upon  cooling,  it  deposits  that  excess  of 
the  dissolved  substance  which  it  only  held  by  virtue  of  its 
high  temperature. 

Some  substances  are  so  easily  soluble,  and  to  such  an  un- 
limited extent,  that  their  solutions  form  crystals  immediately 
upon  cooling ;  others  again  are  taken  up  with  such  difficulty, 
even  at  high  heats,  unless  in  large  bulks  of  liquid,  that  although 
exposed  to  prolonged  ebullition  they  require  to  be  evaporated 
in  order  to  separate  what  has  been  dissolved.  As  the  mode 
of  evaporating  has  an  important  influence  upon  the  form  and 
size  of  crystals,  we  give  some  hints  as  to  the  proper  manner 
of  performing  it. 

If  large  and  well  defined  crystals  are  required,  the  solu- 
tion should  be  subjected  to  spontaneous  evaporation,  for  the 
more  slow  and  uniform  the  concentration,  the  more  regular 
and  gradual  will  be  the  superposition  of  material  required  to 
make  distinct  and  large  crystals.  A  slight  addition  of  solu- 
tion of  gelatin  will,  in  some  instances,  it  is  said,  give  the 
crystals  the  form  of  plates,  as  in  the  case  of  boracic  acid. 

The  solution  should  be  removed  from  the  fire  as  soon  as 
drops,  withdrawn  by  a  glass  rod  and  deposited  upon  a  watch 
glass  or  clean  spatula,  give  small  crystals  upon  cooling.  If, 
however,  a  very  dense  crystallization  is  required,  the  concen- 
tration may  be  continued  until  a  pellicle  forms  upon  the  top, 
but  then  the  solidified  masses  are  confused  and  less  brilliant. 
These  essays  indicate  that  the  liquid  is  evaporated  to  a  point 
22 


830  CRYSTALLIZATION  : — GRANULATION. 

at  which  it  cannot  retain  all  of  its  soluble  matter.  The  ves- 
sels are  then  placed  aside  to  cool  gradually  and  uniformly, 
that  the  excess  may  crystallize  out  of  the  liquid.  The  tem- 
perature should  be  regular,  for  slight  variations  may  alter  the 
form  of  the  crystals. 

Bodies  equally  soluble  in  cold  and  hot  water,  as  well  as 
those  which  are  deliquescent,  require  a  prolonged  evaporation 
as  they  only  crystallize  from  very  dense  solutions. 

When  the  liquid  is  to  be  converted  wliolly  into  solid,  then 
the  process  is  termed  granulation^  and  is  practiced  by  con- 
centrating it  to  a  syrupy  consistence,  removing  the  vessel 
from  the  fire  and  stirring  it  constantly  until  the  mass  has 
cooled  into  granules.  This  mode  is  adapted  for  purifying 
pearl-ash  and  converting  it  into  sal  tartar,  and  also  for  grain- 
ing brown  sugars. 

If  the  liquid,  evaporated  as  above  directed,  becomes  colored 
or  murky  during  the  process  from  partial  decomposition,  it 
may  be  treated  with  bone  black,  and  again  filtered  into  a 
capsule,  or  other  vessel,  previously  warmed  by  a  rinsing  with 
hot  water,  so  as  to  prevent  confused  crystallization  from  sud- 
den contact  with  its  cold  surfaces.  The  blue  stone-ware  cap- 
sules, which  are  made  of  suitable  forms  by  Mr.  Perrine,  of 
Baltimore,  are  far  better  than  porcelain  capsules  or  glass 
beakers,  as  they  are  not  only  more  durable,  but  by  the  rough- 
ness of  their  interior  surfaces  far  more  promotive  of  crystal- 
lization. Stone  basins  for  this  purpose,  called  crystallizers, 
are  made  of  all  sizes,  in  depth  greater  than  in  breadth,  and 
with  a  lip  to  facilitate  the  separation  of  the  residual  liquid 
from  the  crystals.  This  residual  liquid,  called  the  mother 
water,  is  usually  returned  to  the  evaporating  vessel  to  be 
further  concentrated  for  the  production  of  a  new  crop  of 
crystals,  particularly  if  the  liquid  has  been  homogeneous. 

The  first  crop  of  crystals  is  generally  purer  than  subse- 
quent ones,  but  may  still  not  be  sufficiently  free  from  foreign 
salts  and  other  matters,  and,  therefore,  require  to  be  dis- 
solved anew  and  recrystallized  as  at  first.  The  pure  crystals 
are  drained  of  their  mother  water  by  inclining  the  crystal- 
lizer  over  the  evaporating  vessel  long  enough  to  allow  all  of 
the  fluid  to  run  off  at  the  spout.  The  crystals  are  then  re- 
moved with  a  spatula  and  transferred  to  a  drying  frame.  In 
the  first  crystallization  the  mass  of  impure  crystals  are  drained 
upon  a  filter,  and  if  necessary  to  free  them  from  syrupy  or 


PURIFICATION  OF  CRYSTALS.  331 

dirty  liquid,  enclosed  in  a  cloth  and  pressed  (Fig.  276). 
Sometimes,  especially  when  the  crystals  are  not  very  soluble, 
they  may  be  drenched  while  upon  the  filter  with  cold  water, 
which  carries  away  much  soluble  impurity.  This  solution,  if 
valuable,  may  be  mixed  with  the  mother  waters,  and  the  whole 
after  being  transferred  to  the  evaporating  vessel  be  concen- 
trated and  again  crystallized.  The  crop  thus  obtained  is 
very  impure,  and  requires  to  be  drained  on  a  cloth  and 
pressed,  and  subjected  to  as  many  treatments  with  bone  black, 
and  renewed  crystallizations,  as  are  required  to  remove  all 
color.  It  must  be  remembered,  however,  that  bone  black  is 
only  used  when  the  coloring  substance  is  organic,  and  when 
the  characteristic  color  of  the  crystals  is  light,  for  it  has  no 
blanching  action  upon  either  organic  or  unorganized  bodies 
which  are  naturally  tinted. 

In  recrystallizations  only  as  much  water  as  is  necessary  to 
efifect  solution  should  be  used,  so  that  the  mother  waters  may 
be  as  small  in  quantity  as  possible.  The  last  mother  waters 
being  incapable  of  yielding  any  more  crystals,  may,  in  some 
processes,  be  reserved  for  other  purposes ;  as,  for  instance, 
making  new  compounds.  Thus,  for  example,  the  mother 
waters  of  iodide  of  potassium  may  be  used  to  precipitate 
iodide  of  mercury  from  the  bichloride  of  that  metal,  or  of 
lead  from  the  nitrate  of  lead,  and  those  of  chloride  of  barium, 
to  obtain  carbonate  of  baryta  upon  the  addition  of  carbonate 
of  soda. 

Sometimes,  however,  crystallization  is  resorted  to  for  the 
separation  of  one  substance  mixed  with  others  which  are 
variably  soluble  in  the  same  liquid,  and  which  do  not  crystal- 
lize together,  but  separate  from  the  solvent  when  at  different 
densities ; — in  this  case  the  mother  waters  may  contain  one 
or  more  of  the  other  components  of  the  original  substance, 
and  hence  are  not  useful  for  forming  new  compounds  by 
Precipitation.  After  the  separation  of  each  to  the  fullest 
extent  by  crystallization,  at  different  temperature,  the  residue 
of  liquor,  unless  it  be  of  great  value,  may  be  thrown  away. 

As  before  said,  gradual  evaporation  at  a  uniform  tempera- 
ture, and  a  perfect  repose  of  the  concentrated  solution,  give 
the  most  perfect  crystals.  Some  solutions,  however,  crystal- 
lize less  readily  than  others,  and  remain  even  days  and  weeks 
without  exhibiting  any  sign  of  such  tendency.  In  such  cases, 
it  is  advisable  to  agitate  the  mass  slightly  or  to  stir  it  gently 


332  CRYSTALLIZATION  BY  CHEMICAL  REACTION. 

with  a  glass  rod.  This  manipulation  arouses,  as  it  were,  the 
molecules  from  their  inertia,  and  frequently  determines  speedy 
crystallization.  The  resulting  crystals  are  generally,  how- 
ever, confused  and  diminutive. 

To  obtain  large  crystals  from  a  solution  which  is  slow  in 
depositing  them,  it  is  sometimes  proper  to  add  nuclei  to  the 
cold  solution,  these  consisting  of  well  formed  large  crystals 
of  the  same  substance.  As  the  solution  increases  its  density 
by  spontaneous  evaporation,  the  nuclei  assume  a  large  size; 
but  in  order  that  their  enlargement  may  be  uniform  through- 
out, they  must  be  turned  daily,  so  that  the  accumulation  of 
matter  may  take  place  on  all  their  surfaces. 

This  mode,  as  practiced  in  the  arts,  is  somewhat  modified. 
The  deposition  surfaces  are  increased  by  inserting  in  the  solu- 
tion strings  as  nuclei.  When  one  solution  is  thus  exhausted 
of  its  soluble  matter,  the  strings  with  their  surrounding  crys- 
tals are  transferred  to  as  many  fresh  vats  consecutively  as 
are  required  to  give  the  crystals  the  proper  size.  In  this 
manner,  blue  vitriol,  prussiate  of  potash,  tartar  emetic,  and 
rock  candy  are  crystallized. 

When  the  twine  loops  are  replaced  by  slender  twigs  or 
branches  of  wood,  and  the  crystals  are  deposited  in  fine 
flakes  from  bulky  solutions,  the  process  is  termed  arborization. 

Examples  of  arborization,  where,  however,  crystallization  is 
accompanied  by  chemical  or  voltaic  action,  are  furnished  by 
the  various  metallic  trees,  which  are  clusters  of  metallic  flakes 
or  crystals  precipitated  upon  the  surface  of  a  dissimilar  metal 
suspended  in  their  solution. 

Qrystallization  hy  Chemical  Reaction. — The  newly  formed 
compounds,  resulting  from  the  chemical  reaction,  frequently 
assume  the  crystalline  shape.  Thus,  for  example,  antimony 
roasted  in  contact  with  air  forms  crystals  of  antimonious  acid ; 
chlorine  acting  upon  phosphorus  produces  crystals  of  perchlo- 
ride  of  phosphorus.  So,  likewise,  crystals  of  bicarbonate  of 
potassa  are  produced  when  carbonic  acid  is  passed  through  a 
concentrated  solution  of  carbonate  of  potassa. 

Silver  displaced  from  its  solutions  by  zinc  forms  a  crystal- 
line deposit.  Sulphate  of  lime  precipitated  by  alcohol  from 
its  aqueous  solution  also  falls  in  crystals.  Morphia,  also,  and 
other  crystalline  alkaloids,  may  in  like  manner  be  precipitated 
by  decomposing  their  solutions  with  ammonia. 


DESICCATION  ; — OF  SOLIDS.  333 


CHAPTER   XXIII. 

DESICCATION. 

The  desiccation  of  a  substance  consists  in  the  expulsion  of 
its  "  moisture."  The  term  moisture  is  used  only  in  reference 
to  that  variable  amount  of  water,  and  sometimes,  though 
rarely,  of  other  liquids  which  it  may  have  absorbed,  or  other- 
wise retained  in  a  state  of  mechanical  union.  The  combined 
water  or  that  of  crystallization,  of  which  many  bodies  are  in 
part  constituted,  exists  in  an  entirely  different  form,  and  is 
not  usually  to  be  expelled  when  the  drying  is  preliminary  to 
analysis.  When,  however,  it  is  desired  to  dehydrate  a  body 
entirely,  this  latter  water  of  combination  is  also  to  be  dis- 
sipated. 

The  means  of  desiccation  are  various,  and  differ  with  the 
nature  of  the  substance  to  be  dried,  its  quantity,  and  altera- 
bility  by  heat  and  exposure. 

Desiccation  op  Solids. — Undecomposable  salts  and  any 
substances  unalterable  by  air  or  heat,  may  be  dried  by  fusion. 
If  the  amount  of  moisture  is  to  be  determined,  the  crucible 
and  its  contents  should  be  weighed  before  and  after  the  ope- 
ration, the  loss  expressing  the  weight  of  water  expelled. 
Those  bodies,  however,  which  will  not  bear  the  heat  necessary 
for  fusion,  can  be  desiccated  by  evaporation  to  dryness  in  a 
capsule — care  being  taken  to  renew  surfaces  by  constant  stir- 
ring. 

Those  saline  matters  which  readily  yield  all  their  water  by 
exposure  may  be  reduced  to  powder  or  effloresced  by  subject- 
ing them  in  thin  layers  to  a  draught  of  dry  air  which,  if 
necessary,  may  be  moderately  heated.  For  this  purpose  as 
well  as  for  that  of  drying  crystals  which  do  not  effloresce,  it 
is  necessary  in  manufacturing  laboratories  to  have  a  special 
apartment.  This  room  should  be  smoothly  plastered  within, 
and  need  not  be  of  large  size.  As  a  means  of  ventilation  its 
opposite  sides  are  pierced  with  small  holes,  which,  to  prevent 
the  admission  of  dirt,  are  covered  with  wire  gauze.     The  inte- 


334 


DESICCATION  IN  AIR  CHAMBERS. 


rior  is  fitted  with  trellis  shelves  for  the  support  of  the  wooden 
frames,  stretched  over  with  white  muslin,  and  upon  which  the 
substance  rests  between  or  upon,  as  may  be  required,  folds 
of  bibulous  white  paper.  The  heat  is  communicated  by  sheet 
iron  flues  proceeding  from  a  stove  placed  outside  of  the  en- 
closure, or  by  means  of  steam  pipes  fed  by  the  generator, 
Fig.  10.     The  temperatures  should  range  from  75  to  110°  F. 

This  apartment  is  also  useful  for  pharmaceutical  purposes, 
for  drying  plants,  roots,  seeds,  woods,  &c.  They  may  either 
be  suspended  or  spread  in  thin  layers  upon  frames,  and  re- 
peatedly turned  for  the  purpose  of  exposing  fresh  surfaces. 

The  air  chamber,  p.  35,  may,  to  a  limited  extent,  be  made 
to  replace  this  apartment,  and  in  an  experimental  laboratory 
it  is,  together  with  the  means  mentioned  in  this  chapter, 
sufficient  for  all  purposes. 

As  the  salts  effloresced  as  above  still  retain  a  little  water, 
they  require  to  be  repeatedly  pressed  between  the  folds  of 
white  paper  until  dampness  ceases  to  be  imparted  to  them. 
Sometimes  a  previous  trituration  is  necessary  to  facilitate  the 
process. 

Filters  containing  precipitates  after  careful  removal  from 
the  funnel  and  compression  between  the  folds  of  bibulous 
paper,  may  be  further  dried  in  the  same  manner.  Those, 
however,  which  contain  the  results  of  analytic  experiments 
require  more  careful  manipulation.  For  their  treatment  a 
copper-plate  oven  is  often  used.  It  consists  (Fig.  281)  of  a 
brass  soldered  copper  box  7x9  inches,  enveloped  by  a  steam- 
Fig.  281. 


tight  jacket,  in  the  door  of  which  are  vent  holes  for  change 
of  air.  The  water,  or  the  olive  oil  which  is  used  if  the  sub- 
stance requires  a  heat  higher  than  212°  for  its  desiccation, 
is  poured  through  the  centre  aperture  at  the  top,  but  must 
not  more  than  half  fill  the  jacket.     The  lateral  opening  is  for 


DESICCATION  BY  MEANS  OF  BATHS. 


335 


the  reception  of  a  thermometer,  which  is  adjusted  by  means 
of  a  perforated  cork,  for  facilitating  the  regulation  of  the 
temperatures. 

The  watch  glasses,  plates,  or  capsules  in  which  the  sub- 
stances to  be  dried  are  placed,  rest  upon  the  perforated 
shelves  in  the  interior. 

The  thermometer  will  indicate  with  precision  the  tempe- 
rature of  the  bath,  and  care  must  be  taken  that  the  latter  be 
not  allowed  to  exceed  the  degree  above  which  the  body  to  be 
dried  decomposes. 

When  for  any  reason  it  is  deemed  inadvisable  to  remove 
the  filter  from  the  funnel,  they  may  both  be  dried  together 
in  a  hot  air  oven.  Fig.  282.  The  apparatus  shown  in  the  cut 
is  a  copper  double  or  single  cased  cylinder,  with  a 
movable  cover,  to  facilitate  the  introduction  of  the 
substances  to  be  dried.  In  its  centre  is  a  circular 
aperture  for  the  reception  of  the  thermometer  by 
which  the  heat  is  regulated.  A  perforated  dia- 
phragm serves  as  a  support  for  the  funnels,  watch- 
glasses,  capsules  or  other  vessels,  and  in  order  to 
promote  the  evaporation,  a  current  of  air  through 
the  interior  is  excited  by  means  of  the  circular  aper- 
tures in  its  upper  and  lower  circumference. 

These  baths  are  all  heated  over  small  furnaces 
or  preferably  over  the  gas  lamp,  a  uniform  heat 
being  maintained  by  careful  management  of  the 
flame. 

"  Eig.  283  represents  an  arrangement  for  drying  substances 


Fig.  282. 


Fig.  283. 


in  a  current  of  dry  air  produced  by  the  efflux  of  water.     For 


336       DESICCATION  OF  EASILY  ALTERABLE  SUBSTANCES. 

this  purpose  a  known  weight  of  the  substance  is  introduced 
into  the  small  bent  glass  tube  (Fig.  284), 
Fig.  284.  which  has   also  been  weighed  ;   the  body  of 

this  tube  is  plunged  into  a  copper  water  bath 
h,  charged  with  a  saturated  solution  of  com- 
mon salt ;  it  is  kept  in  its  place  by  a  cover 
furnished  with  two  apertures  for  the  arms  of 
the  drying  tube ;  the  wider  arm  is  united  by 
means  of  bent  tubes  and  a  caoutchouc  con- 
nector with  the  U-shaped  tube,  and  containing  fragments  of 
chloride  of  calcium,  and  the  narrow  end  is  connected  with  a 
bent  tube,  which  passes  through  the  cork  of  the  bottle  A 
nearly  down  to  its  bottom.  This  cork  must  fit  the  bottle 
perfectly  air-tight,  and  all  the  joints  and  connections  of  the 
whole  apparatus  must  be  perfect.  The  bottle  A  is  filled  with 
water,  which  on  turning  the  stop-cock  s  flows  out  in  a  small 
stream,  its  place  being  supplied  by  the  air  drawn  through  c, 
and  which  becomes  dried  during  its  passage  through  the 
chloride  of  calcium,  tube  h.  The  bath  is  charged  with  water, 
a  saturated  solution  of  common  salt,  or  of  chloride  of  calcium, 
according  to  the  degree  of  heat  required,  and  it  is  kept  boil- 
ing by  means  of  a  spirit  or  gas  lamp  placed  underneath." 

Desiccation  of  easily  alterable  Substances. — It  has  already 
been  said  that  the  power  of  absorbing  and  retaining  moisture 
varies  in  different  bodies.  This  property  renders  the  use  of 
those  which  have  it  in  the  greatest  degree  available  for  the 
drying  of  others  which  are  deficient  in  it.  The  substances 
subjected  to  this  mode  of  drying  are  mostly  organic  bodies 
and  those  readily  alterable  by  heat  or  exposure,  but  which 
yield  their  moisture  much  below  212°  F. 

This  method  of  desiccation  can  be  conducted  very  well  in 
an  apparatus  consisting  of  a  large  bell  glass,  fitting  accurately 
upon  a  ground  glass  plate  or  bed.  Within  is  a  shallow  saucer 
5,  containing  dry  chloride  of  calcium,  strong  sulphuric  acid,  or 
other  highly  absorbent  material,  and  over  it  a  perforated  glass 
support  a,  upon  which  rest  the  capsules,  crucibles,  beaker, 
watch  glass,  or  other  containing  vessels.  Fig.  285  exhibits 
the  whole  arrangement.  The  rim  of  the  bell,  as  also  that 
part  of  the  plate  which  it  touches,  are  to  be  greased,  in  order 
to  make  the  joint  hermetical.  The  material  thus  exposed  to 
dry  air  continues  to  lose  moisture  until  all  has  been  expelled, 


DESICCATION  OF  EASILY  ALTERABLE  SUBSTANCES. 


337 


or  until  the  absorbent  matter  has  become  saturated ;  in  such 
case  the  latter  must  be  replaced  with  a  fresh  quantity. 

Fig.  285. 


By  substituting  the  bed  of  an  air-pump  for  the  glass  disk 
as  a  support  for  the  other  parts  of  the  apparatus,  otherwise 
arranged  exactly  as  above  described  and  shown  in  the  figure, 
and  increasing  the  evaporation  by  exhausting  the  air,  desic- 
cation proceeds  much  more  rapidly  and  efi'ectually.  A  partial 
vacuum  being  thus  produced  the  drying  substance  liberates 
its  aqueous  vapor  freely,  new  portions  being  given  off  as  soon 
as  those  which  preceded  them  are  condensed  by  the  absorbent 
in  the  saucer,  which  is  usually  in  these  cases  strong  sulphuric 
acid,  that  agent  absorbing  watery  vapors  perhaps  to  a  greater 
extent  than  any  other.  The  process  is  thus  continued  until 
complete  desiccation  of  the  substance  and  saturation  of  the 
absorbent  material  take  place,  the  latter  being  replaced  by 
a  fresh  quantity  when  the  former  has  not  been  completely 
dried. 

If  the  eliminated  vapors  are  corrosive  it  is  advisable  to 
modify  the  arrangement,  so  that  they  may  be  neutralized  as 
fast  as  generated,  otherwise  the  metallic  surfaces  of  the  air- 
pump  will  be  injured.  A  suitable  apparatus  is  shown  in  Fig. 
286.  It  is  an  inverted  bell  glass,  fitted  at  its  neck  with  a 
stop-cock,  by  which  it  connects  with  a  tube  containing  pumice 
stone  impregnated  with  acid  or  alkali,  according  to  the  nature 
of  the  vapors  to  be  absorbed.  The  substance  to  be  dried  and 
the  absorbent  or  hygroscopic  body  are  arranged  within  the 
bell  in  the  usual  manner.     The  latter  is  then  greased  at  its 


3B8 


DESICCATION  IN  VACUO. 


edges,  hermetically  covered  with  a  ground  glass  plate,  and 
exhausted  of  air  by  a  syringe  coupled  with  the  further  end  of 
the  drying  or  chlorcalcium  tube  e. 

Fig.  286. 


By*  having  a  bed  of  ground  glass  instead  of  metal,  and 
detached  from  the  pump  or  syringe,  and  made  to  commu- 
nicate with  it  by  flexible  lead  pipe  and  gallows  screws  only 
when  exhaustion  is  required,  an  apparatus  is  made,  which,  as 
represented  in  Fig.  285,  becomes  available  for  all  the  pur- 
poses of  evaporation  and  desiccation. 

Another  mode  of  drying  alterable  and  fixed  substances  in 
vacuo  is  shown  by  the  arrangement.  Fig.  287,  which  efiects 
a  repeated  change  of  air.     It  consists  of  a  copper  cylinder 

Fig.  287. 


box,  soldered  with  brass,  having  two  apertures  in  its  top, — 
one,  g^  for  the  reception  of  a  thermometer  by  which  to  regulate 
the  temperature,  and  the  other  for  a  glass  tube  g,  the  recipient 
of  the  substance  to  be  dried.  This  tube  is  connected  by 
means  of  a  smaller  glass  tube  2,  tightly  adjusted  in  perforated 


DESICCATION  OP  LIQUIDS.  339 

corks  "with  the  chloride  of  calcium  tube  d,  and  thence  also 
with  the  exhausting  syringe  h.  Heat  being  applied  to  the 
bath*  by  means  of  a  small  furnace  or  gas  lamp  a  partial  vacuum 
is  then  produced  by  several  strokes  of  the  syringe  piston.  In 
a  few  moments  air  is  to  be  admitted  through  the  cocks  c  and  a, 
and  this  exhaustion  and  airing  is  to  be  repeated  at  occasional 
intervals,  the  air  in  its  transit  being  deprived  of  all  moisture 
by  the  chloride  of  calcium.  When  it  is  desired  to  replace 
atmospheric  air  by  carbonic  acid,  hydrogen,  or  other  gas,  it 
may  be  introduced  by  connecting  the  gasometer  containing 
the  required  gas  by  suitable  couplings  with  the  same  appa- 
ratus. 

Desiccation  of  Liquids. — Desiccation  properly  means  the 
freeing  of  a  body,  capable  of  existing  in  a  dry  state,  from 
accidental  moisture.  But  for  the  sake  of  uniformity  of  de- 
scription we  have  applied  the  term  also  to  the  separation,  from 
fluids,  of  water,  which  is  the  ordinary  source  of  moisture.  This 
is  usually  done  by  the  agitation  with  the  liquid  of  some  ab- 
sorbent material,  which  either  unites  with  the  water,  forming 
a  stratum  of  different  density  capable  of  being  separated  by 
filtration  or  decantation;  or  else  combines  with  it  so  firmly 
that  the  fluid  which  is  usually  more  volatile  can  be  separated 
by  distillation. 

Thus  alcohol  and  other  spirits  are  rectified  by  distillation 
over  carbonate  of  potassa,  chloride  of  calcium,  or  free  lime,  it 
being  only  necessary  to  stop  the  process  as  soon  as  the  liquid 
comes  over  slowly,  which  indicates  that  all  the  pure  spirit  has 
passed.  Agitation  of  ether  with  any  of  the  same  absorbents 
produces  similar  results. 

For  analytic  purposes,  and  in  minute  experiments,  liquids 
which  are  less  volatile  than  water  may  be  freed  from  it  by 
exposure  in  open  vessels  under  the  receiver  of  an  air-pump  as 
described  for  solids  in  the  preceding  paragraphs. 

Desiccaton  of  Gases. — Nearly  all  gases  in  the  course  of 
elimination  become  involved  with  more  or  less  moisture,  from 
which  it  is  frequently  desirable  to  separate  them  previous  to 
their  application  to  chemical  reaction.  For  this  purpose  they 
are  passed  over  some  highly  absorbent  material,  such  as  dried 
chloride  of  calcium,  quicklime,  or  sulphuric  acid. 

*  This  bath  is  that  known  as  Rammehberg's  Air  Bath,  which  is  used  alone  for 
drying  substances  inalterable  at  tolerably  high  temperatures. 


340  DESICCATION  OF  GASES. 

The  simplest  arrangement  for  the  purpose  is  given  at  Fig. 
148,  which  exhibits  a  straight  tube  d  d,  containing  the  dried 
chloride  of  calcium,  adapted  at  one  end  by  means  of  a  per- 
forated cork  with  the  gas  generator  A,  and  at  the  other,  in 
like  manner,  with  a  disengagement  tube  e  e.  The  gas  in  its 
transit  through  the  chlorcalcium  tube  is  relieved  of  its  moisture. 
This  tube  varies  in  size  from  half  to  one  inch  diameter,  and 
eight  to  twelve  inches  length,  according  to  the  quantity  of 
gas  to  be  desiccated.  The  chloride  of  calcium  can  be  replaced 
by  quicklime,  potassa,  or  pumice  stone  impregnated  with 
sulphuric  acid,  as  the  nature  of  the  gas  may  require;  but  in 
either  case  the  solid  material  should  be  in  small  lumps.  The 
water  formed  during  the  process  collects  in  this  tube. 

Liebig  uses  the  drying  tube  of  such  a  form  as  is  shown  at 
Fig.  288.     It  differs  from  the  above  in  having  a  bulb,  and  in 

Fig.  288. 


being  drawn  out  at  one  end  to  a  fine  tube,  thus  leaving  but 
one  aperture  to  be  corked.  Lumps  of  absorbent  matter  are 
placed  in  the  bulb,  and  coarse  powder  of  the  same  substance 
in  the  long  part,  each  end  of  which  is  very  loosely  plugged 
with  raw  cotton  to  prevent  the  exit  of  particles. 

For    small    operations  the  bent  form.  Fig.  289,  is  most 
convenient,  as  it  is  easily  adjusted  to  the 
Fig.  289.  mouth  of  the  bottle  without  the  necessity  of 

rp<^"~^        1^^   multiplying  joints.     The  bulbs  in  these  two 
g  latter  tubes  serve  also  as  wells  for  the  recep- 

tion of  the  condensed  vapor. 
Dumas's  vertical  drying  tube,  designed  for  the  desiccation 
of  large  quantities  of  very  moist  gas,  is  so  constructed  that 
the  condensed  vapor  instead  of  remaining  in  contact  with  the 
pumice,  and  thus  impairing  its  absorbent  power,  will  be  de- 
posited in  the  lower  part.  The  tube  leading  from  the  gene- 
rating vessel  is  adapted  by  means  of  a  perforated  cork  to  a 
lateral  tubulure  at  the  base.  The  disengagement  tube  is 
similarly  adapted  to  the  top. 

The  selection  of  the  drying,  or  hygroscopic  material  must, 
as  before  said,  be  made  with  a  regard  to  the  nature  of  the  gas ; 
thus,  for  example,  quicklime  should  never  for  obvious  reasons 


DESICCATION  OF  GASES. 


341 


be  used  for  desiccating  chlorine,  or  other  gases  which  combine 
with  it  chemically ;  for  the  drying  of  nearly  all  such  gases  an 
acid  body  may  be  employed,  and  pumice  stone  in  lumps  of 
about  the  size  of  half  of  a  pea,  impregnated  with  sulphuric 
acid,  is  very  serviceable,  as  it  presents  a  large  extent  of  sur- 
face. For  this  purpose,  however,  the  pumice  must  be  freed 
from  all  the  chlorides  which  it  contains,  otherwise  the  sul- 
phuric acid  will  disengage  muriatic  acid  possibly  to  the  great 
detriment  of  the  gas,  which  is  undergoing  drying.  The  best 
way  is  to  pulverize  and  moisten  it  with  sulphuric  acid,  and 
subject  it  to  calcination  in  a  crucible.  When,  after  constant 
stirring  it  ceases  to  disengage  acid  vapors,  the  operation  is 
finished. 

Anhydrous  phosphoric  acid  is  also  occasionally  employed 
as  a  drier,  but  only  in  very  nice  experiments.  It  is  mixed 
with  clean  asbestos,  which  occupies  the  same  position  in  the 
tube  as  any  of  the  other  absorbents. 

As  a  means  of  perfect  desiccation  it  is  often  required  to 
combine  the  absorbent  powers  of  two  different  materials  in 
one  apparatus,  and  for  this  purpose  the  U  form  of  drying 
tube  is  most  convenient.  It  presents  a  large  extent  of  sur- 
face in  a  limited  space.  There  is,  however,  a  disadvantage 
in  arranging  and  adjusting  its  parts  firmly  together,  and  also 
in  the  necessity  of  occasionally  renewing  the  hygroscopic 
substance  more  frequently  than  in  the  straight  tubes. 

Fig.  290  exhibits  a  proper  arrangement  of  the  U  tubes  for 
the  desiccation  of  gas.  By  this  mode  the  gas  may  be  introduced 

Fig.  290. 


directly  from  the  generating  vessel,  as  shown  at  Fig.  148,  or 
from  a  gas  bag  or  gasometer  as  seen  in  the  drawing  above. 
The  latter  communicates  with  a  pair  of  U  shaped  glass  tubes, 


342  PRECIPITATION. 

which  are  connected  together  by  means  of  bent  tubes,  per- 
forated corks  and  flexible  India  rubber  joints.  In  one  of 
their  legs  is  placed  dried  chloride  of  calcium,  and  in  the  op- 
posite one  asbestos  or  lumps  of  pumice  stone  impregnated 
with  sulphuric  acid.  The  reservoir  on  the  top  of  the  gas- 
ometer being  filled  with  water,  and  its  pressure  applied  by 
opening  the  cocks,  a  stream  of  gas  is  gradually  expelled  and 
in  its  transit  through  the  tubes  is  freed  from  its  moisture  by 
the  absorbents. 


CHAPTER    XXIV. 

PRECIPITATION. 

This  process  is  employed  for  the  immediate  separation  of 
a  body  in  the  solid  state,  both  from  mechanico-chemical  and 
simple  solutions.  The  reagent,  which  is  used  to  produce  the 
action,  is  termed  the  precipitant  and  the  resulting  deposit  the 
precipitate. 

Bodies  in  some  instances  may  be  precipitated  unaltered,  but 
in  most  cases,  being  the  result  of  chemical  reaction,  are  mo- 
dified or  entirely  changed  in  their  nature.  Thus,  for  example, 
sulphate  of  lime  may  be  precipitated  from  its  simple  aqueous 
solution  by  alcohol  and  the  basic  phosphate  of  magnesia  and 
ammonia  by  aqua  ammonise,  they  being  insoluble  in  that  liquid, 
the  addition  of  which  is  also  without  chemical  action  upon 
the  original  solution.  For  like  reasons  the  resins  are  precipi- 
tated from  alcoholic  solutions  by  water;  and  gutta-percha 
from  solution  in  chloroform  by  ether.  If,  however,  carbo- 
nate of  soda  or  other  soluble  carbonate  is  substituted  for  the 
alcohol  then  the  original  combination  is  broken  up  by  the 
action  of  double  elective  affinity,  an  exchange  of  bases  taking 
place,  and  insoluble  carbonate  of  lime  precipitating  instead 
of  the  unaltered  sulphate  as  in  the  instance  with  alcohol.  So 
also,  an  analogous  result  would  ensue  by  virtue  of  simple 
elective  affinity  if  soda  is  used  instead  of  the  carbonate,  the 
lime  then  falling  in  a  free  state,  having  been  deprived  of  its 
sulphuric  acid  by  the  caustic  alkali. 


i 


VESSELS  FOR  PRECIPITATION.  848 

The  consistence  of  the  precipitate  and  its  form  and  color 
vary  with  the  nature  of  the  solutions,  and  the  rapidity  with 
which  it  is  produced.  These  distinctive  features  serve  as 
characteristics  by  which,  in  analysis,  the  presence  of  certain 
bodies  is  determined. 

The  precipitate  is  differently  termed  according  to  its  ap- 
pearance. It  is  flocculent,  when  it  falls  in  small  flakes  or 
flocculae,  like  those  produced  by  ammonia  in  solutions  of  per- 
oxide of  iron;  pulverulent  when  in  fine  powder  and  compact 
like  the  sulphates  of  lead  or  of  baryta;  granular  if  deposited 
in  minute  irregular  molecules;  crystalline,  when  it  subsides 
in  minute  crystals,  as  the  bitartrate  of  potassa,  sulphates  of 
silver  and  of  lime ;  curdy  when  cheesy,  like  that  thrown  down 
by  chloride  of  sodium  from  nitrate  of  silver,  and  gelatinous 
when  of  the  consistence  of  jelly,  as  alumina  freshly  separated 
from  alum  by  carbonate  of  potassa. 

Precipitating  Vessels. — The  most  convenient  vessels,  used 
in  analysis,  are  the  beaker  glasses,  Fig.  254,  or 
wide  mouth  flasks,  Fig.  266,  the  latter  being  used  ^^s-  ^^'• 
only  when  the  process  is  to  be  practiced  upon  the 
boiling  liquid.  When  solutions  are  precipitated, 
especially  for  the  purpose  of  collecting  the  pre- 
cipitates, the  form  of  the  vessel  may  be  that  of 
the  one  in  the  drawing.  Fig.  291,  which  ensures 
the  subsidence  of  all  the  deposit  and  prevents 
particles  from  adhering  to  the  sides.  They  may 
be  of  glass  or  blue  stoneware  according  to  the 
amount  of  liquid  under  process. 

In  chemical  investigations,  the  test  tubes.  Fig.  263,  are  the 
most  convenient  implements.  They  permit  the  operator  to 
use  minute  quantities,  and  they  are  readily  heated  and 
shaken.  As  a  precipitate  is  in  some  instances  not  percep- 
tible for  some  hours,  especially  in  dilute  solutions,  sufiicient 
time  should  be  allowed  to  elapse  before  deciding  upon  the 
reaction  of  a  preciptant  upon  a  solution. 

Directions  for  Precipitating. — Both  the  material  and  re- 
agent must  be  in  solution  and  separately  clarified  by  filtra- 
tion before  being  commingled,  otherwise  the  suspended  mat- 
ters will  subside  with  the  precipitate.  As  heat  generally 
promotes  the  reaction  and  the  subsidence  of  the  precipitate,  the 
solution  should,  in  such  cases,  be  warmed,  or  even  made  hot, 
and  the  reagent  cautiously  added  during  continual  stirring 


344  DIRECTIONS  FOR  PRECIPITATING. 

^ith  a  glass  rod  so  that  all  parts  of  the  liquid  may  be  brought 
in  contact.  The  vessel  is  then  set  aside  upon  a  sand  bath  or 
in  a  warm  place  until  the  deposition  of  the  precipitate  has  left 
the  supernatant  liquor  clear.  A  few  more  drops  of  precipitant 
are  then  added,  and,  if  all  the  matter  has  been  thrown  down, 
they  will  produce  neither  precipitate  nor  cloudiness,  but  if  a 
portion  still  remains  in  solution,  still  more  of  the  reagent 
must  be  added.  The  addition  of  the  reagent  or  precipitant 
must  be  gradual,  for  besides  the  waste  of  material  and  incon- 
venience of  washing  it  out,  an  excess  in  certain  instances  re- 
dissolves  the  precipitate.  As  soon  as  a  drop  or  two  of  reagent 
ceases  to  give  cloudiness  or  precipitate  in  its  descent  through 
the  supernatant  liquid  of  the  settled  solution,  its  addition  must 
be  discontinued  and  the  vessel  placed  aside,  and,  after  suffi- 
cient repose,  subjected  to  decantation  or  filtration  to 
separate  the  solid  from  the  liquid  portion,  the  latter  of  which 
is  also  usually  to  be  reserved  in  analysis  or  when  it  is  of  value, 
as  it  may  contain  other  newly  formed  compounds  dissolved 
in  the  menstruum  employed. 

When  the  precipitate  about  to  be  formed  is  somewhat  soluble 
in  the  liquid  of  the  original  solution,  the  amount  of  that 
liquid  must  be  diminished  by  evaporation,  and  the  precipita- 
tion effected  in  a  concentrated  solution;  for  example,  in  the 
reaction  of  solutions  of  strontia  with  sulphuric  acid  or  solu- 
ble sulphates. 

Metals  may  be  precipitated  from  their  solution  by  other 
metals  having  a  greater  affinity  for  oxygen  than  is  possessed 
by  those  in  combination; — thus  copper  may  be  precipitated 
from  its  sulphate  by  iron,  lead  from  the  nitrate  by  zinc,  and 
silver,  arsenic  and  mercury  from  their  solutions  by  copper. 
A  slight  acidulation  of  the  liquid  facilitates  the  process,  and 
the  metallic  strips  used  as  reagents  must  be  clean  and  bright. 

Metals  are  also  precipitated  by  voltaic  action,  a  familiar 
instance  of  which  is  the  art  of  plating  by  galvanism. 


DECANTATION. — FILTRATION.  345 


CHAPTER    XXV. 

DECANTATION. — FILTRATION. 

Precipitates  which  are  substances  deposited  by  any  means 
from  liquids  in  which  they  have  been  dissolved  or  chemically 
combined,  may  be  separated  either  by  decantation  or  filtra- 
tion. The  first  mode  is  applicable  to  those  solids  which  are 
of  much  greater  density  than  the  menstrua  containing  them, 
and  which  readily  and  rapidly  subside  forming  heavy  com- 
pact deposits.  In  delicate  experiments,  however,  and  in  all 
cases  where  the  liquid  is  turbid  and  deposits  its  suspended 
matter  reluctantly,  the  latter  plan  is  most  appropriate. 

Besides  being  a  process  subsequent  to  precipitation  for 
the  separation  of  the  clear  supernatant  liquor  from  the  sub- 
sident  matter,  decantation  is  also  useful  in  levigation. 
For  WASHING  precipitates  which  require  a  large  amount  of 
water,  or  frequent  renewals  of  the  wash  waters,  it  is  much 
more  convenient  than  filtration.  This  latter  mode,  however, 
must,  as  before  said,  be  always  adhered  to  in  analyses  and 
when  the  precipitate  is  light  and  apt  to  be  disturbed  during 
decantation. 

Decantation  from  small  vessels  in  nice  experiments  is 
practiced  by  gently  inclining  the  vessel  whether  it  be  a 
capsule,  as  at  Fig.  292,  or  a  beaker  glass,  Fig.  293,  and 

Fig.  292.  Fig.  293. 


allowing   the  liquid   to  run  down   in  a   continuous   stream 
along  a  glass  rod  placed  against  its  rim  or  edge.     This  ope- 
23 


346 


DECANTATION  ; — POURINa. 


Fig.  294. 


ration  of  pouring  requires  a  degree  of  dexterity  which  is 
indispensable  in  analytic  operations  in  order  to  avoid  loss  of 
material.  The  exact  position  of  the  rod  is  shown  in  the 
figures.  When  the  pouring  is  completed  the  rod  should  be 
tilted  upwards  for  a  moment,  so  as  to  prevent  the  loss  of  ad- 
herent drops  and  immediately  returned  to  the  vessel,  the  edge 
of  which  should  be  slightly  greased  so  as  to  effectually  pre- 
vent any  particle  of  liquid  from  passing  over.  These  pre- 
cautions are  only  necessary  in  the  decantation  and  filtration 
of  liquids,  during  analytic  processes ;  so  much  care  being  un- 
necessary in  less  important  manipulations,  as  it  is  of  little 
consequence  if  the  liquid  does  carry  over  a  little  of  the  pre- 
cipitate or  suffers  a  slight  loss.  If  the  bulk 
of  liquid  is  very  small,  it  may  be  removed 
with  pipettes.  Figs.  59,  60,  p.  107;  for  larger 
quantities  a  syphon  is  requisite.  This  im- 
plement may  be  of  glass  or  lead  tubes,  the 
former  being  cleanly  and  of  more  general 
application  than  the  latter.  The  shapes 
given  in  the  drawings  refer  to  those  of  either 
material.  The  most  simple  form  is  that 
shown  by  Fig.  294,  being  similar  to  an  in- 
verted V  with  its  opposite  branches  of  un- 
equal length.  The  long  leg  may  be  from 
12  to  20  inches  in  length,  the  shorter  one 
proportionably  less.  The  clear  diameter  is 
from  an  eighth  to  an  half  inch,  according  to 
the  extent  of  the  operation. 

This  syphon  is  inserted  and  filled  with 
water  or  any  other  liquid  which  is  without 
action  upon  that  in  the  vessel,  the  mouth  of  the  longer  leg 
is  then  closed  with  the  finger  and  the  shorter  branch  intro- 
duced, mouth  downwards,  into  the  liquid  to  be  decanted  until 
it  nearly  reaches  to  the  level  of  the  precipitate  without  dis- 
turbing it.  Upon  removing  the  finger  the  liquid  ruif^  out  in 
a  continuous  stream  and  may  be  almost  wholly  drawn  off  by 
slightly  inclining  the  vessel. 

The  rationale  of  the  operation  is  as  follows : — When  the 
short  leg  of  the  syphon  is  dipped  into  water  the  liquid  mounts 
into  the  tube  as  high  as  the  surface  of  that  which  is  in  the 
containing  vessel.  Now  the  weight  of  the  atmosphere^  bears 
equally  upon  the  surface  of  that  in  the  vessel  and  in  the 
syphon,  but  if  the  elastic  force  of  the  internal  air  is  removed 


DECANTATION  ; — SYPHONS. 


347 


Fig.  295. 


or  diminished  by  suction  with  the  mouth  at  the  other  end,  or 
by  having  previously  filled  the  syphon  with  water,  the  liquid 
runs  over,  and  as  the  weight  of  the  column  of  water  in  the 
long  leg  is  greater  than  that  in  the  short  one,  the  flow 
will  be  continuous  while  the  mouth  of  the  short  leg  is  im- 
mersed in  liquid,  for  no  air  can  enter  to  produce  an  inter- 
ruption. 

If  the  liquid  is  not  injurious  or  unpleasant  to  the  taste, 
the  syphon  may  be  inserted  in  the  liquid  without  previous 
filling, — suction  with  the  mouth  at  the  long  end  drawing  it 
over. 

For  the  decantation  of  caustic  liquids  the  syphon  is  fur- 
nished with  a  lateral  tube,  as  shown  in 
Fig.  295,  which  serves  as  a  protection  to 
the  mouth.  Its  application  is  similar  to 
that  of  the  one  described  above  (p.  346); 
the  short  leg  is  dipped  into  the  liquid  to 
be  decanted,  the  lower  end  closed  with  the 
finger,  and  suction  practiced  at  the  orifice 
of  the  supplementary  tube  until  the  air  is 
removed  and  the  liquid  runs  over  and  al- 
most reaches  the  mouth,  when  the  decan- 
tation goes  on  continuously  after  the  with- 
drawal of  the  mouth  and  finger. 

The  annexed  drawing.  Fig.  296,  exhi- 
bits these  syphons  in  operation. 

A   length   of  cotton  wick   doubled  in 
syphon   form,  and   having  its   short  end 


Fig.  296. 


348  filtration; — through  paper. 

immersed  in  the  liquid  also  acts  as  a  syphon,  but  is  much 
slower  in  its  operation. 

The  use  of  the  syphon  allows  the  separation  of  the  liquid 
without  disturbance  of  the  settled  matter,  but  as  the  latter 
still  retains  more  or  less  fluid  which  cannot  be  separated  in 
this  way,  it  may  be  thrown  upon  a  filter  and  in  large  opera- 
tions even  subjected  to  pressure  in  cloths,  as  directed  at  p. 
320. 


FILTRATION. 

The  mode  most  commonly  resorted  to  of  separating  solid 
substances  from  liquids  in  which  they  are  suspended,  is  that 
of  filtration^  and  it  is  also  occasionally  but  rarely  used  for 
the  purpose  of  disuniting  liquids.  The  process  consists  in 
passing  the  mixture  through  suitable  media  of  sufficient 
porosity  to  allow  the  transit  of  the  liquid  portions  while  they 
intercept  any  solid  particles.  For  the  separation  of  liquids 
the  texture  of  the  medium  must  be  such  that  it  is  penetrable 
by  or  attractive  of  the  one,  but  impervious  to  the  other,  of 
them,  as  it  is  upon  this  that  the  success  of  the  operation 
depends;  thus,  for  example,  moistened  paper  will  allow  the 
passage  of  water,  but  not  of  oil. 

Paper,  brown  muslin,  linen,  crash,  woolen  and  canton 
flannel,  felt,  raw  cotton,  sand,  asbestos,  crushed  quartz,  bone 
black — each  and  all  have  their  appropriate  application  as 
media,  and  when  thus  used  are  all  styled  filters  or  strainers — 
the  first  title  being  almost  exclusively  applied  to  those  of 
paper  supported  upon  funnels,  while  the  latter  is  limited  to 
the  other  textures  or  bodies  which  are  either  suspended  upon 
frames  for  pharmaceutical  operations  or  deposited  in  proper 
vessels. 

This  process  is  of  equal  importance  in  chemical  and  phar- 
maceutical operations.  In  analysis  it  enables  us  to  separate 
precipitates  or  insoluble  residue  from  liquids,  and  to  obtain 
each  free  from  particles  of  the  other  —  an  indispensable 
condition  where  both  are  to  be  further  acted  upon  for  obtain- 
ing accurate  results  :  while  in  ordinary  operations  we  can  by 
its  aid  free  liquids  from  dirt  and  other  foreign  matters,  and 
render  them  transparent. 

Filtration  through  Paper. — Paper  is  more  generally 


filtration; — through  paper.  340 

used,  particularly  in  delicate  experiments,  than  any  other 
medium.  It  is  advisable  always  to  use  that  which  is  white^ 
for  it  contains  no  coloring  matter  to  deteriorate  the  liquid 
which  traverses  it.  Moreover,  it  should  he  free  from  saline 
impurities  which  are  soluble  in  acid  or  alkaline  liquids,  other- 
wise the  accuracy  of  analytic  results  may  be  materially  inter- 
fered with. 

The  laboratory  should  be  provided  with  two  qualities  of 
paper,  one  of  fine  quality  for  nice  investigations  and  another 
somewhat  inferior  for  the  less  important  processes.  There 
are  certain  conditions  requisite  in  both  kinds.  They  should  be 
unsized,  yet  strong,  and  while  sufficiently  porous  to  allow  the 
ready  passage  of  the  liquid,  compact  enough  in  texture  to 
retain  all  the  solid  portions. 

'^German  filtering  paper"  answers  very  well  for  all  gene- 
ral purposes,  but  for  analytic  investigations  that  known  as 
"  Swedish"  filtering  paper  is  the  best.  Being  made  expressly 
for  the  purpose  and  of  purified  rags,  it  is  free  from  lime,  copper 
and  salts,  which  have  to  be  removed  from  other  paper  by 
treatment  with  pure  hydrochloric  acid  and  repeated  rinsings 
in  distilled  water  before  it  becomes  fit  for  such  uses. 

The  Swedish  paper  is  whiter  and  thinner  than  the  German, 
and  is  made  with  great  care ;  and  leaves  by  incineration  only 
^J^th  of  its  weight  of  ashes,  an  important  point  in  analyses 
where  the  amount  and  nature  of  the  ashes  left  by  the  paper 
require  to  be  considered. 

The  paper  drawer  should  be  kept  always  supplied  with  a 
stock  of  filters  of  all  the  required  sizes.  The  use  of  the 
Swedish  paper  should  be  limited  to  the  filtration  of  finely 
divided  precipitates.  The  greater  porosity  of  the  German 
renders  it  more  applicable  for  rapid  filtration,  and  as  it  is 
much  less  expensive,  all  large  filters  should  be  formed  of  it. 

The  filters  must  be  circular,  and  cut  by  tin  patterns, 
which  should  consist  of  difierent  sizes  of  2 J,  3,  3 j,  4J,  6,  7 J, 
9,  and  12  inches  in  diameter.  This  mode  of  cutting  different 
sized  filters  from  one  sheet  of  paper,  is  economical  and  saves 
the  waste  which  would  be  occasioned  by  indiscriminate  use  of 
the  paper,  while  many  serious  delays  may  be  prevented  by 
having  a  supply  always  at  hand. 

The  ashes  of  the  piece  of  Swedish  filter  of  each  size,  must 
be  determined  by  incinerating  one  and  accurately  weighing 
the  residue,  and  engraving  its  weight  upon  the  tin  pattern  by 
which  it  is  formed.    Thus,  in  analyses,  we  can  know  by  refer- 


350 


FILTRATION  : — FUNNELS. 


ence  to  the  figures  the  amount  of  fixed  matter  (ash)  in  each 
particular  size.  Kent,  of  New  York,  keeps  the  different 
sizes  for  sale,  put  up  in  neat  boxes  containing  one  hundred. 

The  supports  for  these  circular  filters,  folded  into  conical 
form  as  hereafter  directed,  are  funnels  which  vary  in  mate- 
rial and  form  according  to  the  nature  of  the  operation.  They 
may  be  of  glass,  porcelain,  or  stone-ware.  The  first,  free 
from  lead,  are  of  almost  general  application  for  analytic  pur- 
poses, and  the  latter  two  for  pharmaceutical.  Funnels  of 
metal  are  seldom  required  in  the  laboratory,  a  very  few  in- 
stances only  demanding  the  use  of  lead  or  platinum. 

The  glass  funnels  should  be  made  with  straight  sides,  in- 
clining to  an  angle  of  about  60°.  This 
shape.  Fig.  297,  is  indispensable  for  the 
smaller  funnels  used  in  analyses,  as  it 
forms  in  its  interior  a  true  cone,  which 
allows  the  admission  of  a  larger  amount 
of  liquid  in  a  small  space.  The  pint  fun- 
nels, and  those  of  still  larger  size,  may 
have  an  inclination  of  ten  degrees  less, 
but  if  their  section  has  not  nearly  the 
form  of  an  equilateral  triangle,  the  filters 
fit  badly  and  work  imperfectly.  A  slight 
rounding  off  of  the  angle  at  a,  where  the 
apex  of  the  conical  filter  rests,  greatly 
promotes  the  filtration. 

The  laboratory  must  be  supplied  with  a  series  of  funnels,* 


Fig.  297. 


*  In  addition   to   the   above   there  are  two   other   kinds  of  funnels   used 
for  separating  liquids,  which  have  no  chemical  affinity  and  differ  in  density. 


Fig.  298. 


Fig.  299. 


FILTRATION  : — FUNNELS.  351 

ranging  as  follows,  IJ,  1},  2,  2 J,  3 J,  4 J,  5 J,  and  6 J  inches 
in  the  greatest  diameter  of  the  body  b.  Of  the  smaller  sizes, 
it  will  be  well  to  have  duplicates  or  triplicates  as  they  are  the 
most  frequently  employed.  The  stock  is  not  complete  with- 
out one  or  two  miniature  funnels  of  thin  glass  for  filtering 
into  test  tubes  in  qualitative  investigations ;  and  one  or  two 
of  convenient  size  with  long  barrels  c,  for  charging  retorts 
and  deep  vessels. 

Sometimes  the  glass  funnels  are  ground  at  the  rim,  so  as  to 
be  tightly  closed  by  a  glass  disc,  but  being  expensive  they  are 
only  used  in  rare  instances. 

Funnels  are  sometimes  made  of  porcelain  with  longitudinal 
ribs  in  the  interior  of  the  body,  as  shown  at 
Fig.  300,  for  preventing  the  adhesion  of  the  Fig.  300, 

filter  to  the  sides  in  the  filtration  of  large 
quantities  of  bulky  precipitates.  The  object 
is,  however,  not  effected  by  these  means,  for 
the  paper  sinks  into  the  channels  and  ad- 
heres to  the  surface,  and  still  retards  the 
passage  of  the  liquid.  A  better  way  will  be 
to  use  the  plaited  filters.  Fig.  308. 

Funnels  are  also  made  of  porcelain  and 
more  seldom  of  stone-ware.  They  are  less 
fragile  and  more  applicable  to  the  filtration  of  very  acid  and 
corrosive  liquids,  and  some  other  few  purposes,  than  those  of 
glass;  but  those  of  porcelain  are  not  less  costly.  The  form 
of  those  usually  found  in  the  market  are  shown  in  the  an- 
nexed drawing.  They  are  all  glazed  throughout  and  made 
very  strong,  and  those  used  for  transferring  liquids  from  one 
vessel  to  another  have  the  convenience  of  handles.  In  this 
respect  they  are  preferable  to  the  glass  vessels,  which  by  fre- 
quent rough  handling  are  more  apt  to  be  broken.  Fig.  301 
exhibits  the  form  used  for  acids,  and  Fig.  302  the  same  fun- 
nel ribbed  in  its  interior.  Figs.  303  and  304  present  the 
less  convenient  globular  shape.     Those  shown  at  Figs.  305 

They  are  fitted  with  stop-cocks  in  their  barrels,  as  shown  in  Figs.  298  and  299 ; 
and  one  is  stoppered  also  at  tlie  top  to  prevent  evaporation  when  volatile  liquids 
are  under  process. 

The  mixed  liquids  of  oil  and  water,  or  ether  and  water,  for  instance,  are 
poured  in  the  mouth,  and  after  sufficient  repose  for  the  deposition  of  the  heavier 
of  the  two,  it  can  be  drawn  off  by  opening  the  stop-cock  which  may  be  imme- 
diately closed  as  soon  as  all  has  passed.  The  lighter  liquid  which  is  thus  re- 
tained may  afterwards  be  transferred  in  the  same  way  to  another  bottle. 


352      FILTERS  FOLDED  AND  INTRODUCED  INTO  FUNNELS. 

Fig.  301.  Fig.  302.  Fig.  303. 


Fig.  304. 


Fig.  305. 


Fig.  306. 


and  306,  cullendered  at  the  base,  are  the  most  convenient  of 
all,  being  very  useful  for  draining  crystals,  for  the  filtration 
of  viscous  solutions  through  cloth  filters,  and  for  small  opera- 
tions of  lixiviation. 

Filters  Folded  and  introduced  into  Funnels, — Two  kinds 
of  filters  are  generally  employed,  the  plain.  Fig.  307,  and 
the  plaited,  Fig.  308.     The  former  are  used  in  analyses  and 


Fig.  307. 


Fig.  308. 


whenever  the  suspended  or  precipitated  matters  of  a  liquid 
are  to  be  preserved.  It  is  almost  impossible  to  entirely  re- 
move the  solid  matter  from  the  folds  of  a  plaited  filter,  con- 
sequently such  are  chiefly  applicable  for  the  filtration  of 
bulky  precipitates  from  large  quantities  of  liquid.  This  mode 
of  folding  a  filter  prevents  its  close  adhesion  to  the  glass,  and 
greatly  expedites  the  process  by  increasing  the  surface,  and 


PLAIN  AND  PLAITED  FILTERS. 


853 


by  allowing  a  bubble  of  air  to  ascend  in  the  fold  every  time 
that  a  drop  of  liquid  descends  from  the  filter. 

The  plain  filters  are  folded  as  follows: — 

"  When  a  filtration  is  to  be  performed,  one  of  these  circular 
papers  of  the  proper  size  is  selected  (Fig.  309),  and  then 
doubled  over  one  of  its  diameters  {a  h,  Figs.  309  and  310), 
and  then  over  the  radius  {c  e,  Figs.  310  and  311)  perpen- 
dicular to  the  first  diameter,  so  as  to  form  a  quadrant.     One 

Fig.  310. 


of  the  folds  is  then  opened,  forming  a  hollow  cone,  as  repre- 
sented in  Fig.  313,  which  will  fit  accurately  in  the  funnel,  if 
the  sides  of  the  latter  form  an  angle  of  60°.  If  the  angle  be 
greater  or  smaller,  it  is  necessary  to  double  the  filter  the 
second  time  over  another  radius  {c  f,  Figs.  309  and  312),  not 


Fig.  313. 


Fig.  311.        Fig.  312. 


fie/ 


perpendicular  to  the  first  diameter,  and  then  open  the  large 
or  small  fold  {a  ef,  or  b  of,  Fig.  312),  according  to  the  angle 
of  the  funnel,  and  this  repeated  until  a  coincidence  of  the 
filter  with  the  inside  of  the  funnel  is  effected." 

Fig.  314. 


354 


FILTRATION  : — SUPPORTS  FOR  FUNNELS. 


To  form  the  plaited  filter,  take  a  square  of  paper  and  fold 
it  diagonally,  as  in  Fig.  314 ;  turn  A  upon  B  to  obtain  the 
crease  E  and  open  it ;  then  double  A  upon  E  in  the  same 
direction,  to  make  the  plait  P,  and  double  the  plait  A  back 
upon  F,  so  as  to  form  the  crease  G,  and  holding  this  plait  be- 
tween the  fingers  make  the  fold  between  F  and  D.  Divide 
the  spaces  between  E  B  and  B  D  in  the  same  manner. 

The  filters,  as  above  made,  after  having  their  folds  opened, 
as  at  Figs.  307  and  308,  are  placed  in  the  funnels  and  so 
adjusted  as  to  fit  nicely  to  the  sides.  In  order  to  secure  an 
uninterrupted  flow  of  the  liquid,  and  to  prevent  the  breaking 
of  the  filter,  the  apex  must  not  extend  too  far  into  the  barrel 
of  the  funnel.  Moreover,  the  filter  should  be  a  little  smaller 
than  the  funnel,  for  if  it  reaches  to  the  rim,  evaporation  of 
the  liquid  ensues  from  the  edges,  and  thus,  in  analysis,  may 
be  a  source  of  error. 

The  proper  position  of  the  plain  filter  in  the  funnel  is  shown 
at  Fig.  316,  and  that  of  a  plaited  one  at  Fig.  315. 

In  using  large  funnels  the  filter  may  be  supported  by  a 
plug  of  raw  cotton  placed  in  the  barrel  at  its  junction  with 
the  body. 


Fig.  315. 


Fig.  316. 


The  usual  support  for  funnels  is  the  convenient  portable 
stand.  Fig.  316.  It  consists  of  a  wooden  upright  b,  screwed 
into  a  wooden  bed  plate.     The  arm  a,  which  it  carries,  has  a 


DIRECTIONS  FOR  FILTERING.  355 

circular  aperture  sloping  inwardly  and  downwards,  which  sup- 
ports the  funnel  steadily  in  its  place.  The  screw  c  allows  the 
elevation  or  depression  of  this  arm  at  will,  as  the  height  of 
the  receiving  vessel  beneath  may  require. 

When  the  funnel  is  used  for  transferring  or  filtering  liquids 
into  narrow-mouthed  vessels,  its  barrel  may  be  supported  by 
their  neck;  but  in  order  to  secure  a  free  passage  of  air  it 
should  be  fluted  externally,  or  else  have  a  chip  or  two  placed 
between  it  and  the  inner  sides  of  the  neck,  otherwise  the  con- 
fined air  will  retard  the  process,  and  possibly  force  the  filtered 
liquid,  with  a  hissing  sound,  up  and  over  the  sides  and  mouth 
of  the  bottle. 

After  having  adjusted  the  filter  to  the  funnel,  the  latter  is 
placed  in  the  stand,  so  that  its  barrel  may  rest  against  the 
inner  wall  of  the  receiving  vessel  beneath.  This  position 
allows  the  falling  fluid  to  trickle  quietly  down  the  sides,  and 
prevents  the  splashing  which  would  occur  if  it  fell  directly 
upon  the  surface  of  the  liquid,  and  also  obviates  the  necessity 
of  sinking  the  barrel  far  into  the  receiver. 

The  filtering  apparatus  having  been  thus  arranged,  the 
filter  is  to  be  moistened  with  distilled  water  from  the  bottle, 
(Fig.  38,)  or  when  the  nature  of  the  process  requires,  with  a 
portion  of  the  solvent  liquid,  and  the  excess  allowed  to  trickle 
through,  rather  than  be  emptied  out  by  inverting  the  funnel. 
This  previous  soaking  of  the  filter  greatly  facilitates  the 
operation,  for  dry  paper  absorbs  water  directly,  and  in  the 
case  of  a  turbid  solution,  while  becoming  more  impervious  to 
the  suspended  particles  than  it  would  be  if  the  liquid  which 
contains  them  were  allowed  to  penetrate  at  once  into  the 
filter,  it  gives  also  a  more  ready  passage  to  the  clear  fluid. 
The  edges  of  the  containing  vessel  are  now  to  be  slightly 
greased  in  one  spot,  so  that  in  pouring  there  may  be  no 
adhesion  of  drops  or  trickling  over  the  sides.  It  is  then 
grasped  by  the  right  hand  and  brought  over  the  funnel,  while 
the  left  hand  holds  the  glass  rod  at  a  right  angle  against  the 
edge  of  the  glass  as  shown  in  Fig.  317.  The  end  of  this  rod 
should  merely  reach  the  filter  without  touching  it,  for  fear  of 
abrasion ;  and  the  liquid  should  be  allowed  to  flow  down  its 
length  in  a  gentle  stream  at  first  against  the  sides,  and  as  the 
precipitate  accumulates  it  may  be  allowed  to  fall  in  the  centre, 
as  there  is  then  less  risk  of  splashing.  The  filter  should  never 
be  entirely  filled,  and  as  it  often  requires  many  pourings  to  pass 


856 


FILTRATION  : — POURING. 


the  whole  of  the  liquid,  great  care  must  be  taken  in  returning 
the  rod  to  the  vessel  that  nothing  be  lost.     The  last  particles 


may  be  rinsed  from  the  vessel  and  rod  by  the  jet  of  the  spritz 
bottle  A,*  (Fig.  321,)  by  inclining  both  to  the  positions  shown 

•  The  spritz,  or  washing  bottle,  consists  of  a  twelve  ounce  vial,  to  the  mouth 

Fig.  318. 


of  which  is  adapted,  by  means  of  a  perforated  cork,  a  glass  tube,  drawn  out  at 
its  upper  end  as  shown  in  Fig.  318,  which  represents  at  the  same  time  its  exact 
dimensions.  The  bottle  is  rather  more  than  half  filled  with  water,  and  by 
blowing  into  it  through  the  tube  the  air  is  compressed,  and  when  the  bottle  is 
quickly  inverted  it  forces  out  the  water  through  the  orifice  in  a  strong  jet,  which 


Fig.  319. 


Fig.  320. 


FILTRATION  : — SPRITZ  OR  WASHING  BOTT^LES.  357 

in  the  drawing  below.     If  any  remaining  particles  still  obsti- 
natelj  adhere  to  the  sides  of  the  glass,  or  of  the  rod,  they 

Fig.  321. 


must  be  loosened  by  the  feather  end  of  a  goose  quill,  and  then 
washed  out  as  before  by  the  jet  of  the  spritz.  When  all  the 
liquid  has  passed  through,  the  precipitate  must  be  washed 
down  from  the  sides  of  the  filter  by  the  force  of  the  jet  of 
water  from  the  spritz. 

In  dusty  apartments,  both  funnel  and  receiving  vessels 
should  be  kept  covered  by  circular  or  square  pieces  of  window 
glass.  The  one  over  the  receiver  should  have  an  opening  in 
the  side  for  the  passage  of  the  barrel  or  tube  of  the  funnel. 

The  receivers  are  most  generally  beaker  glasses,  but  cap- 
sules, flasks,  and  narrow  necked  bottles  are  all  made  use  of. 
The  above  precautions  refer  especially  to 
filtrations  in  analytic  operations.     In  larger  Fig-  322. 

operations  the  manipulation  is  not,  neces-  CZT^Z^  ^-^ 
sarily,  so  strict,  and  when  the  dimensions  of     nT    V^^^2^;^^^ 

the  containing  vessel  will  not  admit  of  con-      ^ ^ 

venient  handling  its  contents  may  be  con- 
veyed to  the  filter  by  ladlesfuU  in  the  small  porcelain  dipper, 

may  be  directed  to  any  desired  point.  The  bottle  complete  is  exhibited  at  Fig. 
319.  For  washing  out  beaker  glasses,  or  other  deep  vessels,  a  curved  jet  is 
more  convenient,  and  is  seen  at  a,  Fig.  321. 

When  hot  water  is  required  the  bottle  should  be  of  copper,  of  at  least  a  pint 
capacity,  and  of  the  form  presented  by  Fig.  320.  It  is  heated  as  directed  at 
p.  231,  Fig.  185,  and  to  prevent  burning  of  the  hand,  is  fitted  with  a  non-con- 
ducting handle.  Upon  inversion  of  the  bottle  the  water  is  driven  through  the 
tube  d  in  a.  strong  jet  by  the  elastic  force  of  the  confined  vapor. 


358 


FILTRATION  PROMOTED  BY  WARMTH. 


Fig.  322.  The  ladle,  during  the  intervals  of  the  transfers, 
must  rest  in  a  plate  and  not  be  placed  anywhere  in  the  dust. 
In  order  to  expedite  the  process,  the  liquid,  as  a  general 
rule,  should  be  allowed  sufficient  repose  previous  to  filtration, 
to  deposit  if  possible  all  its  suspended  matter,  and  the  clear 
supernatant  portion  should  be  passed  through  first.  The 
subsident  matter  being  added  last,  is  filtered,  as  it  were,  alone, 
and  offers  no  impediment  by  obstructing  the  pores  of  the  filter 
to  the  passage  of  the  liquid  portion,  as  it  would  if  mixed  with 
it.  As  an  exception  to  this  rule,  certain  precipitates  which 
are  curdy,  gelatinous,  flocculent  or  crystalline,  may  be  filtered 
immediately  after  their  formation.  As  warmth  usually  expe- 
dites the  process,  nearly  all  liquids,  when  circumstances  per- 
mit, should  be  filtered  whilst  hot.* 

*  It  has  already  been  said  that  heat  promotes  filtration;  it  is  even  necessary 
for  saturated  solutions,  which  are  liable  to  deposit  crystals  upon  the  least  dimi- 
nution of  their  temperatures.  Below  are  drawings  of  two  kinds  of  apparatus, 
convenient  for  keeping  liquids  warm  during  the  operation.  Fig.  323  represents 
that  known  as  Professor  Hare's  filter  bath,  and  consists  of  an  oval  copper  jacket, 
flat  at  top  and  bottom,  with  two  conical  apertures  through  its  body.  The  cone, 
with  its  expanded  part  directed  downwards,  is  a  sort  of  chimney,  under  which 
a  spirit  lamp  is  placed  to  heat  the  water  in  the  bath,  and  the  other  is  a  bed  for 
the  funnel.  To  prevent  ignition  of  the  vapors  when  inflammable  liquids  are 
under  process,  there  is  a  partition  beneath. 


Fig.  323. 


Fig.  324. 


The  other  drawing.  Fig.  324,  also  shows  an  apparatus  in  which  there  is  a 
metallic  casing  for  the  support  of  a  funnel.  The  neck  through  which  the  funnel 
passes  is  closed  with  a  perforated  cork,  and  the  contained  water  is  heated  as 
shown  in  the  figure. 

Both  of  these  implements  are  fitted  with  covers. 


FILTRATION  THROUGH  CLOTHS.  859 

For  filtrations  of  heavy  precipitates,  or  a  large  amount  of 
liquid,  it  is  advisable  to  use  the  filter  doubled  or  even  trebled, 
as  it  will  be  thus  enabled  to  resist  a  very  heavy  weight.  This 
precaution  is  necessary  also  when  the  liquid  runs  through  a 
single  paper  turbid.  When  only  the  first  runnings  are  turbid, 
a  single  filter  will  answer  for  small  experiments,  but  the  liquid 
must  be  repassed  through  the  same  medium. 

Filtration  through  Cloths. — In  large  operations,  or 
when  the  solid  matter  to  be  separated  is  too  heavy,  or  would 
corrode  or  clog  the  pores  of  paper,  the  latter  is  replaced  by 
cloth.  The  kinds  of  cloth  vary,  and  each  of  those  already 
mentioned  has  its  appropriate  application.  The  texture  of 
the  medium  must  be  adapted  to  the  consistence  of  the  liquid; 
for  example,  flannel  or  felt  may  be  used  for  filtering  muci- 
laginous, saccharine  and  slightly  acidulous  solutions;  twilled 
cotton  or  canton  flannel  for  oils;  linen  and  muslin  for  tinc- 
tures, vegetable  juices  and  dilute  alkaline  leys.  Sieves  of 
bolting  cloth  are  occasionally  used  for  filtering  liquids  from 
very  fine  or  flocculent  matters. 

Filters  made  of  the  materials  above  mentioned,  and  which 
take  the  name  of  strainers,  instead  of  being  used  like  those 
of  paper,  are  stretched  upon  square  frames  formed  of  four 
pieces  of  lath,  as  shown  at  Fig.  325.     These  frames,  of  which 

Fig.  325. 


there  should  be  several  sizes,  must  be  strongly  jointed,  and 
should  have  inserted  upon  their  upper  surfaces  a  number  of 
rectangular  hooks,  similar  to  those  used  in  the  drying  lofts  of 
calico  factories  for  hanging  up  the  printed  goods.  The  cloth, 
of  whatever  kind,  being  cut  into  a  square  of  size  proportioned 
to  that  of  the  frame,  is  stretched  over  it  somewhat  loosely,  and 
retained  in  position  by  hitching  its  margin  on  these  tacks  or 


360 


FILTRATION  THROUGH  CLOTHS. 


hooks.  This  mode  is  far  preferable  to  that  of  nailing  the 
cloth  down  with  flat  headed  tacks,  for  besides  the  injury  of 
material,  there  is  less  convenience  in  removing  it  after  the 
filtration  for  pressure,  or  for  replacing  it  with  another  when 
it  is  required.  The  support  for  these  strainers' is  an  upright 
stand.  Fig.  326,  the  interval  between  the  legs  of  which  is 
suflScient  to  allow  the  free  entrance  of  the  receiving  vessel. 


Fig.  326. 


Fig.  327. 


When  the  cloths  are  made  into  conical  bags,  as  is  very  often 
the  case,  and  not  without  advantage,  they  are  to  be  suspended 
by  loops  to  a  transverse  beam,  as  shown  in  Fig.  327.  These 
bags  allow  the  convenience  of  using  narrow  mouthed  receivers, 
as  the  liquid  trickles  through  in  a  stream  from  the  most 
depending  parts. 

The  texture  of  the  straining  cloth  must  be  porous,  but 
sufficiently  compact  to  prevent  the  passage  of  any  solid  par- 
ticles. It  is  far  more  convenient  than  paper  for  coarse  filtra- 
tion of  decoctions,  tinctures,  oils,  syrups,  and  for  separating 
liquids  from  solid  organic  matters.  In  most  instances  the 
cloth  or  bag  may  be  renovated  by  washing,  and  thus  be  ren- 
dered fit  for  other  operations. 

Before  stretching  the  cloth  upon  the  frame,  or  suspending 
the  bags,  they  should  be  first  moistened  with  water,  or  if  ne- 
cessary with  a  portion  of  the  solvent  liquor  in  order  to  swell 
the  fibres  and  contract  the  meshes.    The  liquid  should  be  then 


FILTRATION  THROUGH  PULVERULENT  MATTER.  361 

introduced  gradually  without  spilling.     For  this  purpose  a 
tinned,  copper,  or  porcelain  ladle,  Fig.  328,  with  a  wooden 

Fig.  328. 


handle,  is  very  convenient.  A  very  excellent  substitute  is  a 
dipper,  made  from  a  cocoa-nut  shell,  and  sold  in  any  of  the 
furnishing  shops.  Additions  of  liquid  should  be  made  until 
the  filter  is  nearly  full,  and  it  should  be  kept  at  the  same 
level  by  renewing  it  as  fast  as  it  runs  through.  If  the  first 
runnings  are  turbid,  they  should  be  returned  to  the  filter,  and 
if  they  continue  murky,  repassed  through  a  fresh  cloth. 

After  all  the  liquid  has  passed  through  in  this  way,  the 
cloth  or  bag  is  to  be  unhooked,  carried  to  a  table,  securely 
folded,  and  enveloped  in  a  wrapper,  and  subjected  to  pressure 
as  directed  at  p.  320,  for  the  expulsion  of  the  retained  portion 
of  liquid.  The  precipitate  thus  pressed,  when  an  object  of 
value,  is  to  be  cut  up  with  a  spatula  and  spread  on  frames 

for  DESICCATION. 

The  cloths  are  then  to  be  immediately  rinsed  and  cleaned 
in  water  without  soap,  dried  and  placed  away  for  service  at 
another  time. 

Filtration  through  Pulverulent  Matter. — Crushed 
quartz,  clean  white  sand,  asbestos,  bone  black,  and  charcoal 
are  the  materials  generally  used  as  media.  The  two  latter 
act  both  as  filtering  and  purifying  agents,  as  the  liquid  be- 
comes not  only  clarified  in  its  passage,  but  freed  from  color- 
ing and  putrescent  matters,  if  any  exist  in  it.  The  others 
are  used  for  the  filtration  of  very  acid  or  corrosive  liquids, 
which  would  be  destructive  of  paper  or  cloth,  and  partially 
solvent  of  bone  black. 

All  of  these  substances  may  be  used  in  funnels,  a  thin  stra- 
tum being  placed  in  the  bottom  of  the  body,  and  prevented 
from  escaping  through  the  barrel  by  a  loose  cotton  plug  in 
the  neck. 

A  funnel  plugged  in  this  manner,  even  without  the  stratum 
of  pulverulent  medium,  answers  an  excellent  purpose  for  the 
filtration  of  liquids  which  pass  through  freely,  and  whose  sus- 
pended matter  is  in  coarse  particles. 
24 


362  FILTRATION  OF  VOLATILE  LIQUIDS. 

It  will  of  course  be  remembered  that  the  use  of  these  media 
is  only  practicable  when  the  liquid  is  the  sole  object  of  value, 
for  it  would  be  impossible  to  prevent  at  least  the  partial  ad- 
mixture of  the  suspended  matter  with  the  secerning  agent. 

The  asbestos,  sand,  and  charcoal  should  first  be  treated 
with  muriatic  acid  to  remove  soluble  matters,  and  then  tho- 
roughly rinsed  with  fresh  water  to  remove  all  traces  of  acid 
previous  to  their  employment  as  filtering  means.  Freshly 
prepared  and  finely  powdered  charcoal,  by  its  absorbent 
power,  deprives  most  liquors  of  their  fetor  and  organic  co- 
loring matter ;  bone  black  has  the  same  effect,  but  in  a  much 
less  degree.  These  two  are  the  best  substances  for  separat- 
ing impurities  from  syrups  and  aqueous  liquids. 

The  filtering  substance  should  always,  before  being  used, 
be  moistened  throughout,  as  in  displacement,  with  clean  fluid, 
or,  as  is  proper  in  many  cases,  with  the  pure  liquid  which  is 
the  solvent  of  the  various  substances  in  the  fluid  which  is  to 
be  depurated.  Thus  the  substance  in  the  funnel  may  be  made 
to  imbibe  water  before  the  filtration  through  it  of  a  syrup, 
and  alcohol  or  ether  before  the  passage  of  tinctures  or  ethereal 
solutions. 

Where  a  natural  repugnance  exists  between  the  particles  of 
the  fluid  and  of  the  filter,  as  is  the  case  with  finely  divided 
charcoal  of  any  kind  and  water — or  light  aqueous  solutions — 
the  solid  must  be  made  to  absorb  the  first  parts  of  the  fluid  by 
thorough  agitation  and  trituration  with  it,  and  then  be  allowed 
to  separate,  previous  to  its  employment,  by  deposition.  In 
other  cases,  the  pressure  of  a  high  column  of  fluid  upon  the 
substance  must  be  allowed  to  compel  the  necessary  union  of 
surfaces. 

Filtration  by  displacement,  to  which  the  above  mode  is  in 
some  respects  similar,  has  already  been  fully  described  at 
p.  314. 

Filtration  op  Volatile  Liquids. — Donovan  has  con- 
trived an  apparatus  for  filtering  liquids  which  are  vaporizable 
or  alterable  by  exposure  to  air.  It  is  identical  in  principle 
and  construction  with  the  displacer.  Fig.  275,  and  is  very 
useful  for  filtering  alcoholic,  ethereal,  or  ammoniacal  and 
alterable  caustic  liquids. 

The  modification  of  Kiouffe  is  more  convenient  than  the  ori- 
ginal apparatus,  as  it  allows  the  use  of  an  ordinary  funnel  with 
a  cover.     It  is  represented  by  Fig.  329,  and  consists  of  a  glass 


WASHING. 


363 


bottle  A,  with  two  necks ;  into  one  of  which  enters  the  barrel 
of  the  funnel.     The  neck  of  this  funnel  is  loosely  closed  with 

Fig.  329. 


a  plug  of  raw  cotton,  and  the  liquid  is  introduced  through  the 
s  tube  without  uncovering  or  disturbing  the  apparatus.  As 
the  liquid  filters  through,  the  column  of  air  displaced,  finds  a 
vent  through  the  narrow  tube  a,  adjusted  in  position  by  means 
of  perforated  corks.  The  stop-cock  K  allows  the  withdrawal 
of  the  filtrate  at  pleasure. 


CHAPTER   XXVI. 


WASHING. 


In  all  precipitations,  the  powder  thrown  down  becomes 
involved  with  more  or  less  of  the  original  liquid  from  which  it 
has  been  deposited.     As  these  liquid  portions  are  impurities, 


364 


WASHING  OF  PRECIPITATES. 


Fig.  330. 


they  must  be  separated,  and  in  many  large  operations,  and 
when  the  precipitate  is  bulky,  we  effect  their  removal  by 
repeated  washing  and  decantation  ;  but  when  the  powder  is 
light,  and  in  all  cases  where  accuracy  in  estimating  results  is 
required,  the  purification  is  conducted  by  pouring  continued 
streams  of  water  or  other  fluid  through  the  substance  con- 
tained in  the  filter. 

Washing  by  decantation  is  usually  practiced  by  diffusing 
the  precipitate  in  a  large  quantity  of  cold  or  hot  water,  or 
other  suitable  liquid,  as  circumstances  may  require  or  admit ; 
stirring  well,  and  after  sufficient  repose  for  settling,  decanting 
the  clear  supernatant  solution.  A  repetition  of  additions  of 
fresh  water,  and  subsequent  decantations  after  repose,  will  en- 
tirely remove  all  soluble  matter  and  free  the  precipitate  from 
impurity. 

In  analyses,  the  precipitate  is  most  generally  washed  upon 
the  filter  by  projecting  water  from  the  spritz  bottle  A,  Fig.  321, 
the  jet  of  which,  by  its  force,  at  the  same 
time  loosens  that  portion  adhering  to  the 
sides,  and  concentrates  it  all  at  the  bottom, 
when  a  larger  amount  of  washing  liquid 
may  be  added  from  the  bottle.  Fig.  38. 
To  give  force  to  the  issuing  jet,  as  is  some- 
times necessary  in  detaching  particles  from 
the  filter,  the  tubes  of  the  spritz  may  be  as 
shown  in  Figs.  330,  331.  The  compression 
of  the  air  in  the  interior  by  blowing  in  the 
tube  a  produces  a  jet  through  the  lateral 
one  6,  drawn  out  to  a  small  orifice.  This 
form  of  spritz  is  much  more  convenient  for 
large  filters  than  the  smaller  one.  Fig.  319, 
either,  however,  allowing  the  direction  of 
the  stream  to  any  desired  part  of  the  filter. 
The  above  mentioned  bottle  is  flat  bottomed,  and  of  thin  glass, 
so  as  to  answer  for  the  use  of  boiling  liquid. 

The  copper  flask,  Fig.  186,  with  tubes  fitted  to  its  mouth 
as  above  described,  is,  however,  far  more  convenient,  and  less 
liable  to  receive  injury. 

The  precipitate  being  in  this  manner  kept  constantly  min- 
gled with  liquid,  is  soon  freed  from  its  soluble  matter.  The 
latter  fact  is  known  when  a  drop  of  the  wash-liquor,  which 


edulcoration; — washing  bottles. 


865 


has  passed  through,  leaves  no  stain  upon  a  silver  or  platinum 
spatula  heated  over  the  spirit  lamp. 

Fig.  331. 


There  are  many  precipitates  which  require  protracted  wash- 
ing, or  edulcoration^  as  it  is  sometimes  termed,  in  order  to 
cleanse  them  thoroughly,  and  the  bottle  for  the  purpose  is  so 


Fig.  332. 


Fig.  333. 


366  edulcoration; — washing  bottles. 

constructed  as  to  be  self-operating  in  a  measure,  this  mode 
being  a  great  saving  of  time  and  labor  to  the  operator. 
Fig.  332  represents  the  whole  arrangement,  which  is  so  con- 
trived that  by  a  suitably  constructed  tube  J,  adapted  by 
means  of  a  perforated  cork  to  the  flask  or  bottle  a,  the  water 
therein  contained  flows  out  very  gradually,  and  in  quantity 
proportional  to  its  passage  through  the  filter.  The  tube  is 
that  known  as  Gmelin's.  It  is  well  replaced  by  two  separate 
tubes,  which  can  be  readily  formed  over  the  blow-pipe  flame 
by  the  operator  himself;  the  modified  implement  is  shown  at 
Figs.  333,  335. 

Below  are  the  two  forms  of  washing  tubes,  both  acting  upon 
the  same  principle.  Fig.  334  represents  the  one  devised  by 
Berzelius,  and  Fig.  335  that  of  Gmelin's. 

The  mode  of  washing  by  these  bottles  is  very  convenient. 
They  are  nearly  filled  with  water,  and  inverted  over  the 
funnel  in  such  a  position  that  the  part  c  extends  below  the 
surface  of  the  liquid  and  no  further.  The  flow  continues  in 
a  constant  current  without  further  attention  until  the  surface 
of  water  in  the  filter  rises  towards  the  line  ef,  Fig.  335,  and 
diminishes  the  pressing  column,  when  capillarity  is  in  excess 
and  no  more  water  flows.  But  as  the  water  slowly  percolates 
through  the  filter,  the  column  is  increased,  and  the  water  again 
flows.  This  alternate  action  is  continued  until  the  bottle  is 
emptied. 

The  great  convenience  of  this  arrangement  is  that  a  filter 
may  be  washed  during  the  absence  or  inattention  of  the  ope- 
rator. 

If  the  precipitate  is  soluble  in  water,  it  must  be  washed  with 
alcohol,  ether,  or  other  liquid  which  is  without  action  upon  it. 

When  the  bottle  filled  with  water  is  inverted,  as  in  Fig.  332, 
there  will  be  no  efllux  of  water  from  the  small  opening  c,  Fig. 
335,  so  long  as  this  point  is  at  a  certain  distance  below  the 
curve  of  the  syphon;  but  if  the  moistened  finger,  or  other 
body,  be  held  to  the  point  c,  water  will  flow  freely  from  it, 
and  air  bubbles  will  ascend  through  i  h  to  supply  its  place. 
If  the  tubes  and  opening  were  of  large  size,  the  water  would 
flow  out  with  touching  the  end  of  the  tube,  but  being  of  small 
diameter,  and  the  end  c  being  drawn  out  finely,  the  eflSux  of 
water  is  opposed  by  capillary  attraction.  The  column  of  water 
between  e  f  and  g  his  the  force  tending  to  overcome  the  capil- 
lary resistance.     If  this  column  be  lengthened  by  drawing  e  d 


BLOWPIPE  MANIPULATION, 


367 


further  through  the  cork,  then  the  water  will  flow  out  of  e 
spontaneously,     li  cdhQ  pushed  in  just  so  far  that  the  water 


Fig.  334. 


Fig.  335. 


\U 


does  not  flow  spontaneously,  then  the  capillary  resistance 
slightly  predominates.  Then  if  a  substance  to  which  water 
adheres  by  adhesive  attraction,  be  applied  to  the  end  of  <?,  it 
will  make  the  water  flow  so  long  as  it  is  held  there,  because  the 
adhesive  attraction  of  the  touching  overcomes  the  capillary 
action.  1^  c  dhe  thrust  still  further  into  the  cork,  then  capil- 
lary action  predominates  so  greatly  that  no  adhesive  force  can 
counteract  it,  and  the  water  will  consequently  not  flow  out. 
There  is,  therefore,  a  particular  medium  position  for  the  point 
<?,  where  it  will  act  as  desired. 


CHAPTER    XXVII 


BLOWPIPE  MANIPULATION. 


Many  substances  come  under  the  observation  of  the  chemist, 
of  the  nature  of  which  the  physical  properties  furnish  but  little 
indication;  and  as  a  preliminary  examination  called  Qualita- 


368  USE  AND  CONSTRUCTION  OP  THE  BLOWPIPE. 

five  Analysis,  should  in  such  cases  be  made  to  precede  the 
Quantitative  Analysis^ — in  order  that  from  a  knowledge  of  the 
constitution  of  the  body,  a  mode  of  effecting  the  latter  process, 
or  the  determination  of  the  amount  of  its  constituents,  may  be 
devised — it  becomes  very  important  to  be  provided  with  a  means 
of  simple  and  rapid  examination,  and  one  of  general  applica- 
tion. 

Such  means  are  presented  by  the  mouth  blowpipe,  which  is 
simple  in  construction,  cheap,  portable,  and  which  not  only 
furnishes  to  those  who  are  at  a  distance  from,  or  unfurnished 
with  chemical  apparatus,  the  power  of  determining  the  cha- 
racter of  minerals  and  other  bodies,  but  when  employed  as  an 
adjuvant  to  other  methods,  enables  us  frequently  to  appre- 
ciate with  exactness  and  ease  the  most  minute  quantities  of 
simple  bodies,  or  the  ingredients  of  those  which  are  complex. 
Even  in  analyses  in  the  humid  way,  we  are  often  obliged  to 
resort  to  it,  in  order  to  be  enabled  to  ascertain  the  existence 
of  a  substance,  the  presence  of  which  in  solution  cannot  be  de- 
termined by  any  tests. 

The  blowpipe  is  employed  for  the  purpose  of  forcing  a  fine 
stream  of  atmospheric  air  through  the  flame  of  a  candle  or 
lamp,  so  that  the  continuous  current  or  blast  produced,  shall 
impel  in  a  proper  direction,  the  flame,  and  furnish  to  the  par- 
tially burnt  particles  of  carbon  of  which  it  in  a  measure  consists, 
enough  oxygen  to  cause  vivid  combustion  and  great  heat. 
The  simplest  form  of  a  blowpipe,  and  the  one  originally  adopt- 
ed, is  that  used  by  gas-fitters,  jewelers,  and  others,  for 
Fig.  336.  the  purpose  of  soldering,  &c.  It  is  represented  in 
cc-^  Fig.  336,  and  consists  of  a  metallic  tube,  usually  made 
\\  of  brass,  somewhat  curved  at  a  short  distance  from  its 
tapering  extremity.  The  bore  terminates  in  a  very 
small  perforation,  with  a  rounded  margin. 

This  instrument  is  used  by  propelling  a  rapid  and 
steady  blast  of  air  through  the  tube  from  the  mouth, 
by  the  action  of  the  muscles  of  the  cheeks,  and  by 
directing  this  blast  against  the  side  of  the  flame.  The 
blowpipe  of  this  form  is  still  preferred  by  artificers  for 
operations  in  which  little  blowing  is  needed ;  but  when 
the  process  is  of  some  duration,  the  moisture  of  the  breath 
gradually  condenses  in  the  tube,  and  impedes  the  blast,  or  else 
the  latter  forces  some  of  the  aqueous  matter  through  the  flame 
upon  the  substance  which  is  under  examination,  thus  consti- 


wollaston's  blowpipe. 


869 


tuting  serious  objections  to  its  employment  for  analytical 
purposes. 

Of  all  the  modifications  of  this  instrument,  that  of  the  cele- 
brated Gahn  is  by  far  the  best,  and  to  it  almost  universal  pre- 
ference is  given.  Before  proceeding  to  speak  of  it,  however,  it 
may  be  well  to  refer  to  the  ingenious  contrivance  of  Dr.  Wol- 
laston.  It  consists  of  three  pieces,  «,  5,  and  <?,  Fig.  337.  The 
small  end  of  the  tube  a  fits  in  the  large  end  of  h.  The 
latter  is  closed  at  the  other  and  narrower  extremity,  and  a 
short  distance  from  it,  a  small  hole,  dy  is  pierced  transversely 
through  the  tube. 


Fig.  337. 


Fig.  338. 


n  ' 


U 

The  difierent  parts  of  the  instrument  are  represented  to 
better  advantage  in  Fig.  338.  The  smallest  piece,  c,  which 
has  its  short  end  closed,  is  slid  over  the  top  of  5,  by  means  of 
the  oblique  hole  (?,  in  such  a  manner  that  the  small  hole  d  will 


370  gahn's  blowpipe. 

communicate  with  the  fine  conduit  in  the  narrow  end  of  the 
former  piece.  This  instrument  possesses  the  great  advantages 
of  being  compact  and  portable,  for  when  properly  constructed, 
all  its  pieces  will  exactly  fit  in  each  other,  and  when  closed 
the  whole  is  scarcely  larger  than  a  pencil  case.  It  is  shown 
thus  packed  up  in  the  figure.  The  objections  to  it  are  that  it 
contains  no  air  chamber,  or  suitable  reservoir  for  retaining  the 
condensed  moisture,  and  that  the  direction  given  to  the  blast 
in  consequence  of  the  angle  formed  by  the  piece  c  with  5, 
is  such  as  to  prevent  the  operator  from  properly  seeing  the 
substance  of  which  he  is  investigating  the  properties. 

Gahn's  admirable  instrument  shown  in  Fig.  339,  combines 
the  advantages  of  all  former  inventions. 

Fig.  339. 


A  long  and  slightly  conical  tube  fits  in  a  cylindrical  chamber 
which  is  one  inch  in  length,  and  half  an  inch  in  lateral  diame- 
ter, and  which  is  designed  to  condense  and  retain  the  moisture. 
In  the  side  of  this  cylinder  is  inserted  another  and  shorter 
tube,  which  makes  a  right  angle  with  the  large  one,  and  which 
is  considerably  less  in  size.  That  end  of  it  which  is  introduced 
into  the  flame  is  protected  by  a  tip  of  platinum.  This 
Fig.  340.    tip  is  nothing  more  than  a  small  conical  piece  of 

A         platinum,  of  the  form  represented  in  Fig.  340,  which 

^  can  be  placed  over  the  end  of  the  tube,  and  which 
has  a  perforation  as  fine  as  the  point  of  a  needle. 

This  metal  is  preferred  on  account  of  its  infusibility,  and 
of  the  ease  with  which  a  common  impediment  to  the  operation 
— the  clogging  of  the  mouth  of  the  tube  with  finely  divided 
soot — can  be  removed,  when  the  extremity  is  made  of  it.  All 
that  is  necessary  to  get  rid  of  this  deposit,  is  to  subject  the 
clogged  tip  of  the  tube  to  the  action  of  a  high  heat,  produced 
by  the  use  of  the  same  blowpipe,  and  which  burns  ofi"  the 
carbon.  Tips  made  of  silver  answer  a  very  good  purpose,  and 
are  often  used;  but  they  are  apt  to  become  brittle  and  crys- 


MITSCHERLICH  S  BLOWPIPE. 


371 


talline  in  texture  upon  cooling,  after  exposure  to  a  high  red 
heat. 

When  moisture  collects  in  the  chamber  of  this  instrument, 
it  can  be  expelled  by  simply  disconnecting  the  joints,  blowing 
forcibly  through  the  tube,  and  by  the  application  of  a  dry 
cloth. 

Mitscherlich  has  made  an  improvement  upon  Gahn's  blow- 
pipe, which  renders  it  more  portable.  He  reduced  the  size 
of  the  chamber  and  fastened  it  permanently  to  the  long 
tube.  This  tube  is  made  to  unscrew  in  the  middle,  so  that  the 
small  tube  c,  with  its  platinum  jet  D,  can  be  slid  into  the  part 
connected  with  the  chamber,  and  the  other  half  A,  can  be 
fitted  upon  B,  so  that  the  whole  makes  an  instrument  little 
inferior  in  portability  to  Wollaston's,  as  shown  at  F.  The 
little  nozzles  adjusted  upon  these  instruments*  can,  in  a  mea- 
sure, be  dispensed  with  if  care  is  taken  to  remove  the  blowpipe 
from  the  flame  the  moment  the  blowing  is  suspended.  When 
the  small  orifice  becomes  filled  with  soot  it  can  be  reopened 
by  introducing  the  point  of  a  needle,  which  has  been  held  for 
a  short  time  in  the  flame.  If  this  latter  precaution  is  not 
attended  to,  the  point  is  apt  to  snap  off,  and  sometimes  great 


Fig.  341. 


Fig.  342. 


difficulty  is  experienced  in  removing  it,  and  risk  incurred  of 
injuring  the  instrument. 


They  are  preferred  for  cheapness,  and  should  be  silvered  or  platinized. 


372 


ECONOMICAL  BLOWPIPE. 


Dr.  Black's  is  the  most  cheap  form  of  metallic  blowpipe, 
and  is  shown  in  Fig.  342.  It  is  a  conical  tube  of  japanned 
tinned  iron  plate,  closed  at  the  wide  extremity;  near  which, 
upon  the  side,  is  adapted  a  brass  tube  with  a  nozzle  of  proper 
size. 

Silver  and  tinned  iron  are  the  proper  materials  for  the 
construction  of  blowpipes.  Copper,  brass,  and  German  silver 
are  employed,  but  being  exposed  both  to  heat  and  moisture, 
they  oxidize  easily,  and  give  an  unpleasant  odor  to  the  hands 
and  brassy  taste  to  the  mouth. 

Necessity  may  compel  the  student  to  make  a  blowpipe  of 
his  own  construction.  In  such  a  case,  a  common 
Fig.  332.  clay  tobacco  pipe  may  be  converted  into  one  by 
closing  the  bowl  with  a  cork,  in  which  is  fitted  a 
glass  tube,  with  one  end  drawn  out  to  a  small 
orifice.  It  is  economical  and  convenient,  and 
considering  the  fragile  material  of  the  exit  tube, 
answers  the  purpose  admirably. 

One  of  the  best  blowpipes  we  have  ever  seen 
employed  was  constructed  in  this  way,  except 
that  the  small  tube  was  made  by  filling  the  end 
1 '^^--^         of  the  bore  of  a  broken  tobacco  pipe,  firmly  with 
\..^/ci^      common  putty,  and  then  piercing  the  plug  thus 
made  with  a  pin  or  needle,  and  allowing  it  to  dry. 
This  expedient  succeeds  very  well,  and  although  the  instru- 
ment is  clumsy  in  appearance,  the  extremity  is  not  fusible 
like  glass,  and  with  a  little  skill  the  whole  may  be  so  fashioned 
as  to  make  a  most  serviceable  apparatus. 

Entire  blowpipes  are  also  readily  made  from  glass  tubes. 
The  material  is  cheap,  and  the  requisite  form  can  be  easily 
given  them;  but  notwithstanding  these  advantages,  their  use 
is  very  limited,  in  consequence  of  their  brittleness,  and  the 
ease  with  which  the  point  of  the  small  tube  fuses. 

The  blast  from  the  blowpipe  is  directed  upon  the  flame  of  a 
wax  or  tallow  candle  with  a  cotton  wick,  or  that  furnished  by 
coal  gas  or  an  oil  lamp.  If  a  candle  is  employed,  Bergmann 
directs  that  the  wick  be  inclined  to  one  side  towards  the 
object,  i.  e.  in  the  direction  in  which  the  flame  is  to  be  im- 
pelled. Besides  not  always  giving  sufiicient  heat,  candles 
have  the  disadvantage  of  consuming  too  rapidly,  since  the  wax 
or  tallow  readily  melts  from  the  heat  which  is  radiated  from 
the  substance  in  the  flame.     The  wick  also  requires  frequent 


BLOWPIPE  LAMP  AND  APPLIANCES. 


373 


trimming.  The  lamp  recommended  by  Berzelius,  with  the 
improvements  of  Harkort,  gives  the  best  flame  for  these  ex- 
periments, and  has  a  very  convenient  form.  It  is  seen  in 
Fig.  344.     It  is  made  of  brass,*  has  a  length  of  4 J  inches,  is 

Fig.  344. 


|fi^^^ 


of  a  slightly  conical  shape,  and  is  an  inch  in  diameter  at  the 
lower  end,  which  is  furnished  with  a  screw  to  adjust  it  to  the 
brass  rod,  which  is  fastened  to  metallic  cross  pieces,  so  as  to 
support  it  in  its  perpendicular  position.  The  screw  enables 
the  operator  to  raise  or  lower  the  lamp  to  suit  his  convenience. 
On  the  upper  side  of  the  lamp,  at  one  end,  is  an  opening  for 
pouring  in  the  oil,  closed  by  a  screw  cap  with  a  leather  washer. 
Near  the  other  end  is  the  wick  holder,  a  piece  of  tinned  iron 
of  a  rectangular  form,  which  is  inserted  in  a  brass  screw  per- 
manently connected  with  the  lamp.  The  direction  of  the 
wick  holder  is  parallel  with  the  lamp.  When  not  in  use  a 
screw  cap  with  a  washer  is  adapted  to  the  corresponding  screw, 
and  surrounds  the  wick,  closing  it  hermetically,  so  as  to  prevent 
.the  escape  of  oil  in  transportation.  The  object  of  the  obliquity 
of  the  front  of  the  lamp  is  to  permit  a  considerable  deflection 
of  the  flame  when  it  is  desired  to  bring  the  assay  nearer  to 
the  source  of  heat,  as  is  sometimes  necessary.  Fig.  345 
represents  the  cap  covering  the  wick,  and  gives  a  view  of  the 
position  of  the  cross  pieces  forming  the  support  of  the  lamp. 


Tin  plate  may  be  substituted. 


374 


BLOWPIPE  : — FLAME. 


Fig.  345. 


The  rod  can  be  unscrewed  in  the  middle,  the  cross  pieces 
disunited,  and  all  the  parts  separated,  so  that  the  whole  can 
be  packed  away  and  made  to  occupy  very  little  space. 

This  lamp  is  fed  with  pure  olive  or  refined  rape  oil,  which 
is  decidedly  the  best.  For  the  stationary  blow- 
pipe table  in  the  Laboratory,  coal  gas  is  used, 
and  is  supplied  by  a  leaden  pipe  with  a  nozzle 
of  brass,  similar  in  form  to  the  wick  holder  of 
the  lamp ;  it  does  not  furnish  the  same  amount 
of  carbon  for  combustion  as  the  above  named 
liquids,  but  is  preferred  on  account  of  its  clean- 
liness. The  triangle.  Fig.  344,  with  the  bars , 
attached  to  the  arm  which  moves  laterally, 
by  a  screw  capable  of  being  moved  upon  the 
upright,  is  for  the  support  of  vessels,  such  as 
small  crucibles,  over  the  flame.  Different  sized 
crucibles  can  be  made  to  fit  in  this  triangle  by 
removing  one  or  more  of  the  bars. 

In  some  cases  the  common  spirit  lamp.  Fig.  115,  before  de- 
scribed, is  used  to  furnish  the  flame.  It  answers  particularly 
well  for  the  heating  of  glass  tubes  when  it  is  desirable  to  avoid 
a  deposit  of  soot  upon  the  surface. 

The  Flame, — The  flame  of  a  common  candle  or  oil  lamp  con- 
sists of  four  distinct  parts.  The  part  within  a  b, 
Fig.  345,  surrounding  the  wick  at  the  point  where  it 
commences  to  burn,  of  a  beautiful  blue  color,  which 
becomes  thinner  as  it  ascends  from  the  wick,  and  a 
small  distance  from  it  disappears  entirely;  a  very 
dark  central  portion  c,  having  a  conical  shape  and 
surrounded  by  c?,  the  brilliant  part  of  the  flame 
through  which  the  former  is  distinctly  seen ;  and, 
finally,  the  external  faintly  luminous  lamina,  a  and 
h,  which,  becoming  broader  near  the  apex  of  the 
flame,  envelops  the  whole. 

These  different  appearances  are  accounted  for 
in  the  following  way.  The  wick — which,  after  its 
combustion  has  melted  the  upper  portion  of  the 
fatty  matter,  is  merely  the  agent  for  the  imbibi- 
tion and  passage  upwards  by  capillary  attraction,  of  the 
fluid  combustible — gives  off  at  its  ignited  extremity  the  in- 
flammable gases  and  possibly  some  carbon,  into  which  the 
fat  has  been  resolved.     These  gases,  not  meeting  with  a  suflS- 


Fig.  346. 


BLOWPIPE  : — FLAME.  B75 

cient  supply  of  oxygen,  rise  and  form  the  central  dark  cone; 
upon  the  outer  surface  of  which,  however,  the  hydrogen  con- 
tained in  them  may  be  supposed  first  to  combine  with  the 
oxygen  of  the  air,  to  the  production  of  an  intense  heat,  by 
exposure  to  which  the  carbon  which  had  been  unconsumed  is 
heated  to  whiteness;  the  latter  thus  forming  the  brilliant 
luminous  portion  of  the  flame  by  its  ignition,  and  more  or 
less  complete  union  with  oxygen.  The  external  envelope  of 
faintly  luminous  matter  is  probably  owing  to  the  complete 
combustion  in  contact  with  air,  of  those  portions  of  gaseous 
matter  which  had  not  been  previously  burnt.  This  part, 
considered  in  reference  to  its  whole  surface,  is  the  hottest 
portion  of  the  flame,  but  the  maximum  of  heat  is  given 
ofi^  at  the  level  of  //  in  the  Fig.,  and  from  that  part  it  gra- 
dually decreases  to  the  apex  and  the  base.  The  combustion 
of  a  little  carbonic  oxide,  and  possibly  some  carburetted 
hydrogen,  gives  rise  to  the  blue  portion  of  the  flame  seen  at 
a,  h.     This  is  the  coolest  part  of  the  flame. 

A  stream  of  air  projected  into  the  flame  makes  it  present 
a  very  difi*erent  appearance.     Before  the 
nozzle  of  the  blowpipe,  is  formed  a  blue,  ^^s-  347. 

well  defined,  long  and  slender  cone,  which  /^      •^ 

is  similar  in  appearance  to  that  in  Fig.  346.  ^E^ 

The  hottest  point  in  the  flame  thus  excited 
is  just  before  the  point  of  the  cone.  Exte- 
rior to  it  is  a  yellowish-brown  flame  a  c, 
somewhat  luminous,  but  undetermined  in 
outline.  It  is  in  this  flame  a  little  beyond 
the  point  of  the  blue  cone,  that  reduction  is  effected.  For 
oxidation  we  must  remove  the  body  from  the  outer  flame  just 
so  far  as  the  temperature  is  consistent  with  the  object  in  view, 
i.  e.  at  such  a  distance  in  advance  of  the  inner  flame,  as  is  best 
calculated  to  oxidize.  But  as  metals  differ  in  their  affinity 
for  oxygen,  this  point  can  only  be  ascertained  by  practice. 

The  former  is  called  the  reducing  flame,  because  in  conse- 
quence of  an  excess  at  its  extremity,  of  burning  carbonaceous 
matter,  which  greatly  absorbs  oxygen,  the  oxide  of  a  metal, 
if  employed,  is  deprived  of  its  oxygen,  or  in  other  words,  is 
reduced  to  the  metallic  state.  One  object  of  the  blow-pipe  is 
to  supply  oxygen,  which  is  always  contained  in  air  expelled 
from  the  lungs,  so  as  to  burn  off  the  hydrogen  of  the  flame 
and  to  set  free  the  carbon  and  carbonic  oxide  in  order  to  re- 


376 


THE  MANNER  OF  HOLDING  THE  BLOWPIPE. 


duce  the  reducible  body  exposed  to  its  action.  It  is  also  the 
co-operation  of  some  unconsumed  carburetted  hydrogen  that 
assists  in  the  reduction. 

The  Manner  of  Holding  the  Blowpipe. — The  cut,  Fig. 
348,  represents  somewhat  imperfectly  the  proper  mode  of 

Fig.  348. 


holding  the  blowpipe  and  support,  and  of  directing  the  flame 
upon  the  object  on  the  latter.  The  former  is  held  like  a  pen 
between  the  thumb  and  first  two  fingers  of  the  right  hand, 
and  its  mouth-piece  is  inserted  between  the  lips.  The  sup- 
port is  held  in  a  convenient  position  by  the  left  hand,  and 
both  arms  should  be  so  fixed  upon  the  elbows,  or  otherwise, 
without  reference  to  a  particular  fashion  of  holding  them,  as 
to  ensure  that  the  object  be  kept  constantly  in  one  place 
under  the  continuous  blast  from  the  blowpipe. 

The  Blast. — A  uniform  current  of  air  is  expelled  through 
the  tube  from  the  lips,  by  making  the  mouth  and  lungs  act 
upon  the  same  principle  as  the  ordinary  table  blowpipe,  which 
has  been  before  fully  described.  The  lungs  acting  like  the 
piston,  force  by  their  alternate  contraction  and  dilatation,  an 
intermitting  current  of  air  into  the  cavity  of  the  mouth  ;  which 
being  analogous  to  the  condensing  box  of  the  large  blowpipe, 
by  the  constant  pressure  and  elasticity  of  its  muscular  walls, 
converts  the  alternating  into  a  continuous  blast.     The  be- 


BLOWPIPE  MANIPULATIONS  : — SUPPORTS.       377 

ginner  finds  great  difficulty  in  properly  regulating  this  part 
of  the  process,  and  some  never  acquire  the  necessary  tact.  It 
is  an  accomplishment  which  experience  and  practical  instruc- 
tion alone  can  give,  and  which  no  description  can  impart. 
The  blast  is  first  forced  through  the  tube  by  filling  the  mouth 
with  air,  expanding  the  cheeks,  and  then  keeping  up  a  con- 
stant and  forcible  pressure  with  the  muscles  forming  their 
parietes,  at  the  same  time  that  respiration  through  the  nose 
is  allowed  to  go  on  calmly  and  uniformly  as  usual.  But  as 
the  current  constituting  the  jet  is  required  to  be  uniform,  it 
must  be  prevented  from  sharing  in  the  alternating  impulse 
communicated  from  the  lungs,  by  a  valve-like  closure  of  the 
opening  of  the  mouth  into  the  throat ;  which  closure  becomes, 
with  a  little  practice,  an  instinctive  act.  When  the  mouth  is 
nearly  emptied  of  its  air,  this  communication  is  temporarily 
reopened  without  any  intermission  of  the  blast,  the  cavity  is 
refilled,  and  the  communication  again  closed  until  the  next 
occasion  for  its  opening. 

Supports. — The  substance  under  examination,  must  be  al- 
lowed to  rest  firmly  upon  a  support,  which  should  be  such  as 
will  not  fuse  under  a  high  heat,  combine  chemically  with  the 
fused  body,  or  prevent  its  complete  heating  by  rapid  conduc- 
tion. The  supports  in  most  common  use  are  charcoal,  and 
platinum  either  in  the  state  of  wire  or  foil. 

Charcoal  makes,  for  many  operations,  an  excellent  support, 
especially  that  kind  of  it  which  is  made  from  well-grown  pine 
wood  or  the  branches  of  the  willow.  It  should  be  well  charred, 
and  that  which  snaps  or  smokes  in  the  fire  should  be  rejected. 
It  is  desirable  that  it  should  be  as  free  as  possible  from  ashes, 
which  nearly  always  contain  a  trace  of  iron  and  manganese; 
therefore  dense  and  compact  woods  should  not  be  used,  as  they 
give  much  ashes,  and  often  contain  a  considerable  amount  of 
those  oxides,  which  by  uniting  with  the  fluxes  employed,  would 
give  incorrect  results.  Straight  pieces,  free  from  knots,  should 
be  sawn  in  the  direction  of  the  fibres,  into  oblong  supports  of 
the  proper  size.  The  assay  is  placed  in  a  shallow  concavity 
made  near  one  end  of  such  a  support  by  the  borer  or  point  of  a 
knife ;  and  upon  this  substance,  so  prepared,  oxidation,  reduc- 
tion and  fusion  are  chiefly  performed. 

Sometimes  the  reducing  property  of  charcoal,  and  the 
rapidity  with  which  it  is  (Sssipated  into  carbonic  acid,  inter- 
25 


378  BLOWPIPE  MANIPULATIONS  : — SUPPORTS. 

fere  with  the  result.  In  such  cases  platinum  in  the  form  of 
foil  or  wire  is  used.  A  narrow  strip  3  inches  long  and  J  inch 
broad  is  often  advantageously  employed  for  oxidation.  The 
substance  which  is  to  be  oxidized,  is  placed  on  it  near  one  end, 
and  heat  is  applied  by  the  blowpipe  flame  upon  its  under  side. 
Its  conducting  power  is  so  inconsiderable  that  the  other  end  may 
be  held  between  the  fingers  without  inconvenience.  Platinum 
cannot  in  general  be  used  for  reduction,  as  it  forms  fusible 
alloys  with  some  of  the  metals ;  nor  should  sulphurets,  arse- 
niurets,  &c.,  be  heated  in  contact  with  it.  When  the  strip  is 
too  short  to  be  held  between  the  fingers,  it  can  be  inserted  in  a 
piece  of  wood  or  charcoal,  or  be  held  between  the  points  of  the 
pincette.  A  small  spoon  of  the  same  metal  is  sometimes 
made  use  of;  but  in  the  majority  of  cases  the  wire  may  be 
substituted  for  any  other  means. 

When  platinum  wire  is  used,  it  should  be  moderately  thin, 
and  have  a  length  of  about  2J  inches,  and  should  be 
Fig.  349.  bent  into  a  hook  at  one  end,  which  serves  as  the  sup- 
1  port  for  the  assay.  This  part  is  either  heated  for  a 
moment  in  the  flame  or  moistened  by  the  tongue,  and 
dipped  into  the  flux,  whereby  a  small  quantity  becomes 
attached,  which,  when  fused  to  a  transparent  bead  by 
the  blowpipe  flame,  becomes  firmly  fixed  in  its  bed 
and  occupies  the  space  within  the  curve.  The  side  of 
the  bead  is  then  mi)istened  and  a  little  of  the  assay 
is  made  to  adhere  to  it. 
Both  are  now  fused  together,  and  the  appearance  of  the 
bead  held  in  one  or  the  other  part  of  the  flame,  in  reference 
to  opacity,  color  and  other  characteristics,  can  be  distinctly 
seen  from  all  sides,  and  in  this  way  are  colorations  of  the 
bead  by  metallic  oxides  particularly  to  be  distinguished.  The 
only  objection  to  this  hooked  wire,  occurs  in  the  case  of  the 
use  of  fusible  flux,  which  is  apt  to  fall  through  it.  Two 
or  three  additional  turns  of  the  hook  will  generally  make  a 
bed  suflficiently  close  to  prevent  this  salt  from  running  through 
when  fused. 

The  bead  can  be  detached  from  the  wire,  when  cold,  by  a 
slight  blow  with  the  hammer.  If,  after  its  removal,  the  wire 
is  not  left  perfectly  clean,  a  bead  of  soda  may  be  fused  upon 
it,  and  afterwards  dissolved  out,  when  it  takes  the  impurities 
with  it.  In  extensive  investigations  by  means  of  the  blow- 
pipe a  number  of  these  wires  should  be  provided. 


DETECTION  OF  VOLATILE  SUBSTANCES. 


879 


Detection  of  Volatile  Substances  by  means  of  the  Blow^ 
pipe. — When  volatile  substances  or  gaseous  products  are  to 
be  tested  by  means  of  this  instrument,  the  body  to  be  ex- 
amined is  usually  exposed  to  heat  in  an  open  glass  tube,  which 
may  be  from  two  to  four  inches  in  length,  and  from  the 
twelfth  to  the  third  of  an  inch  in  diameter.  The  body  is  placed 
near  to  one  end  and  the  blast  is  directed  upon  it,  while  the 
tube  is  inclined  more  or  less  in  proportion  to  the  current  of 
air,  which  is  required  to  be  passed  through  it.  By  such 
means,  disengaged  vapors  may  be  sometimes  recognized  as 
they  emerge  from  the  upper  end,  and  volatile  matters  con- 
densed upon  a  part  of  the  tube. 

It  is  often  necessary  to  deposit  the  substance  in  the  angle 
of  a  curved  tube  so  as  to  prevent  it  from  falling  out.  A  tube 
so  bent  is  shown  at  5,  Fig.  351.     Another  modification  is  re- 


Fig.  350. 


Fig.  351. 


quired  where  the  access  of  much  or  any  air  would  counteract 
the  intention  of  the  operator,  by  oxidating  the  body.  In  such 
cases  the  lower  end  of  the  tube  is  either  completely  closed, 
or  drawn  out  to  a  fine  orifice  as  at  c  in  the  same  figure.  A 
tube  of  this  form  is  well  adapted  to  the  sublimation  of  sele- 
nium from  a  sulphuret,  where  the  entrance  of  much  air  would 
oxidize  it.  Decrepitating  substances  should  also  be  heated 
in  tubes  closed  at  one  end,  and  should  be  so  inclined  as  to 
avoid  loss  of  particles.  For  such  and  many  other  purposes 
tubes.  Fig.  168,  enlarged  into  a  bulb  at  one  extremity  are 
very  appropriate. 

All  the  glass  tubes  and  vessels  employed  in  this  way  should 
be  perfectly  free  from  lead. 

The  following  instruments  are  also  used  in  making  examina- 
tions with  the  blowpipe.  Steel  forceps  with  the  points  made  of 
platinum,  for  holding  the  assay  in  the  blowpipe  flame  to  as- 


380 


INSTRUMENTS  USED  IN  BLOWPIPE  ANALYSIS. 


certain  its  fusibility  or  other  properties  when  exposed  to  an 
elevated  temperature.  The  two  upper  figures  of  the  cut  re- 
present different  views  of  an  excellent  forceps,  capable  of  very- 
general  application.  Two  strips  of  steel,  with  narrow  pla- 
tinum points  6,  h,  are  fastened  in  the  middle  by  a  piece  of 
metal  seen  at  e,  e.     These  strips  separated,  as  seen  in  the 

Fie.  nr>g. 


figure,  constitute  a  double  pair,  one  being  at  a,  a,  and  the 
other  at  e.  The  platinum  points  by  the  elasticity  of  the 
metal  of  which  the  forceps  are  made,  are  always  closed.  To 
open  them  it  is  only  necessary  to  compress  with  the  thumb 
and  finger,  the  small  projections  with  the  button  heads  d,  d, 
which  are  connected  with  the  strips  opposite  to  them.  Upon 
relaxing  the  pressure,  the  assay  is  forcibly  held  between  the 
points.  The  points  a  a  are  tempered,  and  are  used  for  de- 
taching exceedingly  small  fragments  of  the  mineral. 

Another  form  of  this  instrument  is  employed,  but  its  use  is 
not  quite  as  convenient  as  that  of  the  one  just  mentioned.  Its 
points  b  c  are  also  of  platinum,  but  curved  a  little,  as  repre- 
sented in  the  figure.  The  legs  are  made  of  brass.  The  for- 
ceps is  kept  open  by  the  elasticity  of  the  metal,  and  closed 
by  a  double  button  d,  which  slides  up  and  down  in  a  slit  cut 
in  the  legs.  As  brass  is  a  good  conductor  of  heat,  two  pieces 
of  wood  e  e  are  fixed  to  the  legs,  by  which  the  instrument  is 
held,  to  prevent  any  inconvenience  to  the  hand.     Under  this 


INSTRUMENTS  USED  IN  BLOWPIPE  ANALYSIS.  381 

last  forceps,  is  still  another  made,  of  iron,  which  can  be 
used  for  a  variety  of  operations,  and  which  is  not  solely  con- 
fined to  this  application.  Substances  to  be  held  very  firmly 
are  placed  between  the  points.  It  has  a  button  d  d,  with  a 
steel  spring  d  e,  to  prevent  the  forceps  from  opening  by  the 
sliding  back  of  the  button. 

A  Microscope. — A  plano-convex  microscope,  with  two  lenses 
of  different  magnifying  powers,  is  often  useful  in  minute  ana- 
Fig.  353. 


lysis,  and  one  is  i*epresented  in  Fig.  353,  which  is  made  to 
fit  in  a  small  receptacle.  By  its  aid,  the  minute  structure  of 
bodies,  and  fine  colors  imparted  to  the  fluxes  or  to  charcoal, 
which  often  deceive  the  naked  eye,  are  examined. 

Charcoal  Borer. — A  conical  tube  of  tinned  iron  with  the 
margin  filed  to  a  sharp  edge,  for  making  cavities  in  the  char- 
coal support,  is  often  made  to  occupy  a  place  in  blowpipe 
apparatus.  It  answers  very  well  as  a  case  to  contain  a  phial 
as  shown  in  the  figure  above. 

A  pair  of  cutting  pliers  is  used  to  clip  off  small  particles 

Fifr.  354. 


of  minerals,  and  pieces  of  a  metal  or  alloy  for  examination, 
and  for  many  other  purposes  which  will  suggest  themselves 


382 


INSTRUMENTS  USED  IN  BLOWPIPE  ANALYSIS. 


to  the  experimenter.     A  clasp  is  attached  to  the  handles  for 
the  purpose  of  keeping  them  forcibly  closed. 

The  Hammer  and  the  Anvil, — A  polished  hammer  of  hard- 
ened steel,  Fig.  355,  with  a  square,  even  surface  at  one  end. 

Fig.  355. 


Fig.  356. 


and  the  other  terminating  in  an  edge  with  sharp  corners,  is  a 
very  necessary  implement.  The  flat  surface  is  very  appli- 
cable for  flattening  globules  of  reduced  metals,  and  the  edge 
for  breaking  off"  small  pieces  of  minerals.  Very  small  frag- 
ments can  be  broken  ofi*  without  doing  any  injury  to  the  re- 
maining portion,  which  is  often  kept  as  a  specimen. 

A  necessary  accompaniment  to  the  hammer  is  the  anvil, 

which  is  represented  in  Fig.  356, 
in  a  most  convenient  and  com- 
pact form.  It  is  made  of  steel, 
and  is  usually  about  three  inches 
long,  one  inch  in  thickness  and 
five-eighths  of  an  inch  in  breadth, 
and  any  one  of  its  surfaces  can 
be  used.  The  substance  to  be 
broken  up,  or  the  metallic  globule  to  be  flattened  out,  is  enclosed 
in  thin  paper,  and  having  been  placed  upon  the  anvil,  is  struck 
with  the  hammer  until  the  proper  effiect  is  produced.  If  the 
substance  is  reduced  to  powder,  the  paper  prevents  any  of  it 
from  being  scattered  or  lost. 

The  Mortar  and  Pestle, — These  implements,  made  of  agate, 
are  of  small  size,  and  have  been  described  at  page  79.  They 
should  be  hard  and  perfectly  free  from  holes  and  cracks,  or 
they  will  be  liable  to  fracture  and  to  the  filling  up  of  their 
crevices  with  the  powdered  materials — much  to  the  detriment 
of  future  operations. 

An  Electroscope  and  Magnetic  Needle  Case. — A  cylin- 
drical wooden  box  is  used  to  contain  Haiiy's  electroscope  and 
a  magnetic  needle. 


INSTRUMENTS  USED  IN  BLOWPIPE  ANALYSIS.  883 

The  former  consists  of  the  hair  of  a  cat,  Fig.  357. 

insulated  by  being  inserted  in  sealing  wax  I 

poured  into  the  bore  of  a  small  glass  tube.  r-^ 

This  tube  is  fastened  in  a  wooden  screw,  <!=> 
which  closes  one  end  of  the  case.     It  is  so 


^ 


delicate  that  a  very  small  quantity  of  elec- 
tricity is  discovered  by  its  aid.  On  bring- 
ing it  near  to  an  excited  body,  it  is  attracted  by  it ;  but  if  ne- 
gative electricity  is  developed  in  it,  by  rubbing  or  drawing  it 
rapidly  through  the  fingers,  and  it  is  then  brought  in  proximity 
to  the  excited  body,  it  will  be  attracted  or  repelled  in  accord- 
ance with  the  existence  in  that  body  of  positive  or  negative 
electricity.  In  the  screw  at  the  other  end  (each  one  serving 
as  a  stand),  is  fixed  a  similar  tube  and  sealing  wax  to  insu- 
late a  small  steel  pin,  which  supports  a  magnetic  needle  con- 
tained in  the  box.  The  needle  is  mounted  with  an  agate  cup 
to  prevent  friction  as  much  as  possible,  when  suspended  on 
the  point  of  the  pin.  In  this  condition,  it  is  used  to  indicate 
the  presence  of  iron  when  it  exists  in  a  mineral  in  an  appre- 
ciable quantity,  and  also  the  magnetic  condition  of  iron  ores. 
Minerals,  before  and  after  being  submitted  to  the  action  of 
the  blowpipe,  should  be  examined  in  regard  to  these  pro- 
perties. 

A  Steel  Magnet. — This  is  employed  in  the  mode  recom- 
mended by  Haiiy  to  ascertain  whether  the  slightest  trace  of 
magnetic  force  exists  in  minerals,  and  consequently  whether 
the  metals  in  which  that  force  exists  are  present.  The  expe- 
riment is  thus  performed.  The  magnet  is  placed  at  a  small 
distance  from  a  suspended  magnetic  needle,  its  north  pole 
being  directed  towards  that  of  the  needle ;  it  is  then  gently 
moved  around  the  needle  until  the  latter  takes  a  position  at 
right  angles  to  its  former  place,  owing  to  the  repulsion  of  the 
same  kind  of  magnetism.  This  repulsion,  and  the  force  of  ter- 
restrial attraction  which  tends  to  make  the  needle  return  to  its 
former  direction,  now  hold  the  needle  exactly  balanced  between 
them,  so  that  the  smallest  disturbing  magnetic  force  moves  it 
out  of  its  place.  In  this  way  an  amount  of  magnetic  influence 
may  be  detected,  which  would  not  be  sufficient  to  affect  the 
needle  in  its  ordinary  state.  In  performing  this  experiment, 
care  must  be  taken  not  to  excite  electricity  in  the  mineral  by 
friction,  as  that  force  might  affect  the  result  more  or  less. 

A  knife  of  good  hardened  steel  is  used  for  trying  the  com- 


384  INSTRUMENTS  USED  IN  BLOWPIPE  ANALYSIS. 

parative  hardness  of  metallic  bodies  and  minerals  generally. 
It  may  be  used  as  a  charcoal  borer,  and  if  well  magnetized 
can  be  substituted  for  the  magnet.  The  point  is  used  to  take 
up  the  fluxes  before  mixing  them  in  the  palm  of  the  hand  with 
the  mineral  which  has  been  pulverized  for  examination. 

Files  are  convenient  for  detaching  small  particles  of  a  metal 
which  is  to  be  investigated,  cutting  glass  tubes,  and  for  trying 
the  hardness  of  bodies.  They  may  be  of  different  shapes, 
and  should  be  kept  clean  and  out  of  the  reach  of  corrosive 
vapors. 

An  Edulcorator  or  spritz.  Fig.  319.  This  is  used  to 
wash  the  charcoal  from  the  reduced  metal.  It  is  necessary 
to  be  very  cautious  in  doing  this  when  the  metal  is  small 
in  quantity,  as  the  force  of  the  jet  may  carry  the  latter  away 
with  the  charcoal.  A  pipette  or  dropping  tube,  made  by 
drawing  out  in  the  flame  of  a  candle  or  spirit  lamp  one  end 
of  a  glass  tube  to  a  small  opening,  can  be  used  with  more 
impunity.  The  separation  will  be  facilitated  by  reducing  to 
powder,  in  the  agate  mortar,  the  charcoal  adhering  to  the  piece 
of  metal,  as  the  globule,  if  malleable,  will  be  thus  slightly  flat- 
tened and  made  more  distinctly  visible. 

Small  capsules  of  porcelain  or  watch  glasses,  are  useful  for 
receiving  temporarily  the  results  of  the  experiments ;  such  as 
specimens  of  reduced  metal,  the  colored  beads,  &c.,  and  for 
keeping  separately,  different  fragments  of  the  minerals  to  be 
investigated. 

A  small  pair  of  scissors,  a  thin  saw  with  fine  teeth  for 
sawing  pieces  of  charcoal,  a  pair  of  small  tongs  for  holding 
crucibles,  &c.,  over  the  spirit  lamp,  a  small  capsule  of  plati- 
num, a  touchstone  with  needles  of  gold  and  alloys  of  different 
standards  for  trying  the  fineness  of  gold,  will  all  be  found  of 
occasional  use. 

Fig.  358. 


The  Box  containing  the  Reagents. — As  it  is  necessary  to 
have  the  fluxes  always  ready  for  use,  Gahn  contrived  a  con- 


BLOWPIPE  MANIPULATION  :    THE  REAGENTS.  385 

venient  and  portable  box  for  the  purpose,  which  is  seen 
in  Fig.  358.  It  is  8 J  inches  long,  1/g  broad,  1  inch  in 
height,  and  is  divided  into  nine  compartments  to  receive  the 
different  reagents.  Each  division  has  a  lid  nicely  closing  its 
particular  box  so  as  to  prevent  any  one  substance  from  becom- 
ing mixed  with  the  others.  A  common  lid  closes  over  these 
smaller  ones  and  is  fastened  to  the  box  by  two  hooks.  The 
cross  pieces,  which  are  permanently  fixed  to  the  large  lid,  fit 
into  spaces  between  the  2d  and  3d  lids  from  each  end,  and 
serve  to  make  them  more  secure.  If  more  reagents  are  re- 
quired than  can  be  contained  in  these  boxes,  those  which  are 
but  seldom  used  may  be  wrapped  in  paper  and  placed  in  one 
of  them. 

The  Reagents. — The  reagents,  which  must  all  be  chemically 
pure,  are  the  following: — 

Carbonate  of  Soda,  commonly  called  soda,  which  is  much 
used  to  detect  the  presence  of  silica,  to  assist  the  reduction  of 
metallic  oxides,  and  generally,  to  determine  whether  a  body 
unites  with  it  to  the  production  of  a  fusible  compound. 

Cyanide  of  Potassium. — This  substance  being  very  deli- 
quescent, should  be  kept  as  free  as  possible  from  contact  with 
humid  air,  and  had  better  be  placed  in  a  small,  tightly  corked 
test  tube,  which  may  have  its  place  in  one  of  the  small  com- 
partments of  the  box. 

As  a  blowpipe  reagent,  cyanide  of  potassium  is  highly  use- 
ful; its  action  is  indeed  extraordinary.  Substances  like  per- 
oxide of  tin,  sulphuret  of  tin,  &c.  &c.,  which  for  their  reduc- 
tion with  carbonate  of  soda,  require  rather  a  strong  flame,  are 
reduced  with  the  greatest  facility  when  cyanide  of  potassium 
is  used.  In  blowpipe  experiments  we  always  use  a  mixture  of 
equal  parts  of  carbonate  of  soda  and  of  cyanide  of  potassium, 
since  the  latter  alone  fuses  too  easily.  This  mixture,  besides 
its  more  powerful  action,  has  another  advantage  over  carbonate 
of  soda :  it  is  with  extreme  facility  imbibed  by  the  porous  char- 
coals, so  that  the  purest  metallic  globules  are  obtained. 

Bihorate  of  Soda. — This  salt,  which  is  commonly  called 
borax,  is  used  to  facilitate  the  fusion  of  very  many  substances. 
When  melted  with  the  metallic  oxides,  its  bead  assumes  a 
great  variety  of  colors,  which  furnish  excellent  indications  of 
the  presence  of  the  metals. 

Phosphate  of  Soda  and  Ammonia. — This  substance,  called 
also  microcosmic  salt,  phosphorus  salt,  and  fusible  flux,  is  of 
very  general  application,  and  as  it  dissolves  most  of  the  me- 


386      BLOWPIPE  MANIPULATION  :  THE  REAGENTS. 

tallic  oxides  with  great  readiness,  the  colors  produced  in  its 
bead  are,  if  possible,  more  brilliant  and  characteristic  than 
those  made  with  borax. 

Nitrate  of  Potassa,  or  saltpetre,  is  used  to  assist  in  the 
oxidation  of  metals,  as  it  yields  up  its  oxygen  very  readily 
when  exposed  to  heat. 

Bisulphate  of  Potassa  in  solution,  is  used  to  indicate  lithia, 
boracic  acid,  nitric  acid,  fluohydric  acid,  bromine  and  iodine ; 
and  also  for  the  separation  of  baryta  and  strontia  from  other 
earths  and  metallic  oxides. 

Vitrified  Boracic  Acid  (glass  of  borax)  is  used  to  detect 
the  presence  of  phosphoric  acid ;  also  small  portions  of  copper 
in  alloys  of  lead. 

Fluoride  of  Calcium  (fluor  spar),  when  mixed  with  bisul- 
phate  of  potassa,  serves  to  detect  lithia  and  boracic  acid. 
Alone  it  is  a  test  for  gypsum. 

Sulphate  of  Lime,  or  gypsum,  in  the  form  of  plaster  of 
Paris,  is  sometimes  used  as  a  reagent  with  fluoride  of  calcium. 
Nitrate  of  Cobalt. — This  very  valuable  test  is  used  in  a 
somewhat  concentrated  solution. 

Alumina  heated  in  the  oxidating  flames,  after  being  moist- 
ened by  a  drop  or  two  of  this  solution,  acquires  a  beautiful 
pale  blue  color;  magnesia  a  rose  red  tint,  and  zinc  a  bright 
green.  The  solution  is  contained  in  a  phial  similar 
Fig.  359.  to  the  one  represented  in  Fig.  359.  The  glass  stop- 
ple, tapering  to  a  point,  descends  into  the  solution, 
so  that  on  withdrawing  it,  a  small  quantity  adheres 
to  its  extremity.  Berzelius  uses  a  cork  stopple  with 
a  platinum  wire  flattened  out  in  the  form  of  a  spoon, 
at  the  end  which  is  immersed  in  the  solution.  The 
phial  may  be  of  such  a  size  as  to  be  conveniently 
received  in  the  charcoal  borer,  page  381.  Oxalate  of 
cobalt  may  be  made  to  take  its  place,  and  as  it  is 
used  in  powder,  it  is  often  of  more  convenient  application. 

Nitrate  of  Nickel  in  solution,  or  Oxalate  of  Nickel  in  pow- 
der. The  oxide  of  nickel  gives  a  brown  color  to  soda  glass, 
while  potash,  if  melted  with  a  substance  containing  it,  ac- 
quires a  bluish  purple  color.  A  bottle  similar  to  the  one  just 
described  may  contain  the  solution  of  the  nitrate. 

Lead,  very  pure,  and  especially  free  from  silver,  is  used  in 
cupellation. 

Bone  ashes  are  employed  in  cupelling  metals  containing 
gold  and  silver,  or  some  of  the  ores.     The  cupels  are  prepared 


BLOWPIPE  MANIPULATION  :   THE  REAGENTS.  387 

by  moistening  a  small  quantity  of  the  ashes,  mixed  with  a 
little  soda  salt  to  make  it  coherent,  and  by  kneading  the  mass 
in  the  palm  of  the  left  hand  to  the  consistence  of  a  stiiff  paste. 
A  cylindrical  hole  made  in  a  piece  of  charcoal  is  then  filled 
with  the  paste,  and  after  the  surface  is  smoothed  with  the 
small  agate  pestle,  a  slight  depression  is  made  in  the  centre, 
sufficiently  large  to  hold  the  metal  or  mineral  to  be  cupelled, 
together  with  a  small  quantity  of  the  proof  lead.  The  cupel 
is  slowly  dried  by  heating  it  carefully  in  a  stove  or  over  the 
flame  of  a  spirit  lamp.  The  assay  with  the  lead  is  then  placed 
on  the  cupel  and  submitted  to  the  action  of  the  exterior  or 
oxidating  blowpipe  flame.  By  the  influence  of  this,  the  lead 
is  oxidized,  and  the  fused  litharge  so  formed,  is  absorbed  by 
the  bone  ashes,  while  the  silver  or  gold  is  left  behind  in  the 
form  of  a  brilliant  globule ;  which,  before  its  complete  purifi- 
cation, exhibits  the  iridescence  formerly  described  under 
CuPELLATiON.  Plattner  describes  a  convenient  instrument 
for  making  the  cupels. 

Oxide  of  Copper  is  used  for  the  purpose  of  detecting  chlo- 
rine. 

Silicic  Acid^  when  melted  into  a  fusible  glass  with  soda,  is 
a  test  for  sulphur  or  sulphuric  acid.  The  assay  must,  how- 
ever, not  contain  it. 

Silver^  in  the  form  of  wire  or  foil,  is  made  use  of  for  ascer- 
taining the  presence  of  sulphuret  of  potassium,  or  any  other 
soluble  sulphuret. 

Tin  Foil  sometimes  assists  in  the  reduction  of  metallic 
oxides,  which  are  dissolved  in  a  bead  of  one  of  the  fluxes,  and 
by  its  use  we  sometimes  get  a  more  satisfactory  result  than  is 
obtained  without  it.  For  instance,  when  a  small  quantity  of 
copper  is  dissolved  in  a  bead  of  borax,  or  of  microcosmic  salt, 
and  the  glass  is  treated  in  the  reducing  flame,  it  sometimes  be- 
comes ruby  red  and  opaque.  But  if  the  amount  of  copper  is 
so  small  that  the  reducing  flame  cannot  produce  this  result,  a 
little  tin  added  to  the  bead,  and  heated  with  it,  makes  the 
proper  appearance  evident  immediately  upon  its  cooling. 

Iron  wire,  which  is  generally  that  metal  in  its  purest  state, 
precipitates  some  other  metals  from  the  difi^erent  fluxes,  or 
separates  therefrom,  sulphur  and  the  fixed  acids.  It  is  also 
used  to  reduce  phosphoric  acid  to  phosphorus,  which  com- 
bining with  iron,  forms  a  white  brittle  metallic  globule,  the 
phosphuret  of  iron. 

Besides  the  above  mentioned  tests,  it  is  proper  to  have 


388 


BLOWPIPE  TABLE. 


Formate  of  Soda,  which,  when  anhydrous,  is  used  to  detect 
arsenic  in  oxide  of  antimony.  Test  papers  colored  with  lit- 
mus, Brazil  wood,  and  turmeric,  are  also  convenient. 

The  substances  mentioned  in  the  foregoing  list  as  reagents 
are  all  of  those  which  are  essential  to  the  completeness  of  the 
blowpipe  apparatus.  While,  however,  occasions  may  arise 
for  the  use  of  any  or  all  of  them,  the  great  majority  of  exa- 
minations with  the  blowpipe  can  be  made  with  the  aid  of  but 
a  few,  and  the  possession  of  the  first  four  or  five  upon  our 
list,  with  the  fluid  nitrate  of  cobalt  and  the  metals  referred 
to,  may  be  considered  as  quite  enough  to  make  the  manipu- 
lator competent  to  pursue  ordinary  investigations. 

Blowpipe  Table, — In  the  Laboratory  all  the  instruments 
essential  to  the  expedition  of  blowpipe  analysis  are  placed 
within  convenient  reach  of  the  operator.  For  this  purpose 
Gahn's  table,  which  has  drawers  both  in  the  side  and  front, 
will  be  found  very  useful.  The  side  drawers  are  divided  into 
many  compartments,  and  are  shown  in  Fig.  360,  drawn  out 
from  their  usual  position.     The  right  hand  drawer  contains 

Fig.  360. 


the  apparatus  most  frequently  used,  and  the  left  that  which  is 
less  often  required.  The  lamp,  blowpipe,  fuel,  wick  and  other 
necessaries  of  a  rougher  kind  occupy  those  in  front. 

This  table,  although  quite  small,  may  be  found  to  take  up 
too  much  room.  Berzelius'  case,  which  is  much  more  porta- 
ble, may  then  be  substituted  for  it.     It  consists  of  a  neat 


BLOWPIPE. — THE  TRAVELING  CASE.  889 

mahogany  case,  exhibited  in  Fig.  361,  which  has  a  cover,  and  is 
14  inches  long  and  9J  inches  wide.  Each  article  is  made  to  fit 
closely  in  a  corresponding  cavity,  so  that  it  is  kept  firmly  in 

Fig.  361. 


its  place.  It  contains  all  the  necessary  apparatus  for  these 
experiments,  and  scarcely  occupies  more  space  than  an  ordi- 
nary portfolio.  It  is  neatly  put  up  by  Kent,  in  New  York, 
with  the  apparatus  and  tests,  after  directions  given  by  Ber- 
zelius. 

Traveling  Case. — Although  Berzelius'  case  occupies  little 
space,  and  can  readily  be  introduced  into  a  common  trunk, 
many  mineralogists  prefer  having  their  blowpipe  apparatus 
enclosed  in  a  still  more  compact  form.  The  traveling  case 
is  arranged  very  much  in  the  same  way  as  the  large  size  of 
surgical  instrument  cases,  and  consists  of  a  piece  of  leather 
forty  inches  or  more  in  length,  with  sides  capable  of  being 
folded  down  upon  the  body,  and  long  strips  of  the  same 
material  tacked  along  its  centre,  so  as  to  leave  open  spaces  for 
the  insertion  of  the  various  pieces  of  apparatus.  After  these 
latter  have  been  deposited  in  place,  the  lateral  folds  are  closed 
upon  them,  and  the  whole  is  rolled  up  and  tied  with  tape,  or 
brought  together  with  a  common  strap  and  buckle. 

It  is  advisable  to  place  the  largest  instruments  near  that 
end  of  the  case  which  is  first  rolled  up.  When  blowpipe 
operations  are  in  progress,  the  case  can  be  unrolled  and  sus- 
pended from  a  nail  in  a  wall,  so  that  free  access  can  be  had 
to  all  its  contents. 

Besides  the  various  parts  of  apparatus  which  we  have  been 
describing,  it  is  well  that  the  operator  should  be  provided  with 
a  piece  of  sheet  iron  twelve  inches  or  more  in  diameter,  and 
with  a  rim  turned  up  around  the  margin.     This  may  be  placed 


890 


BLOWPIPE  : — THE  TEST  SERIES. 


upon  the  table,  under  the  lamp,  and  will  serve  to  retain  ignited 
or  other  particles  thrown  off  from  the  substance  which  is  un- 
der examination.  A  sheet  of  white  paper  placed  over  it  will 
enable  the  experimenter  to  discover  with  ease,  minute  par- 
ticles which  might  otherwise  be  lost. 

It  will  be  well  for  the  chemist  to  supply  himself  with  a  set 
of  chemically  pure  tests  which  may  be  kept  in  small  stop- 
pered vials.  Such  a  series  is  very  useful  as  affording  the 
means  of  comparing  the  behavior  of  a  mineral  with  that  of 
the  substance  supposed  to  be  an  ingredient  of  it,  and  of  thus 
verifying  results.  Its  possession,  moreover,  conduces  to  the 
attainment  of  dexterity  in  manipulation,  and  of  the  knowledge 
of  the  various  reactions  occurring  under  the  blowpipe  flame. 

The  set  may  consist  of — 


Alkalies 

Baryta 

Strontian 

Lime 

Magnesia 

Alumina 

Glucina 

Yttria 

Zirconia 

Thorina 

Silica 

Acids  of  Arsenic 

Vanadic  acid 

Molybdic  acid 

Tungstic  acid 

Oxide  of  chrome 

Antimony  and  its  oxides 

Oxide  of  tellurium  and  telluric  acid 

Tantalic  acid 

Titanic  acid 

Oxides  of  uranium 

Oxides  of  cerium 

Oxide  of  lantanium 

Oxide  of  didymium 

Oxide  of  manganese 

Oxide  of  zinc 

Oxide  of  cadmium 


Oxide  of  iron 

Oxide  of  cobalt 

Oxide  of  nickel 

Bismuth  and  its  oxide 

Oxides  of  tin 

Oxide  of  lead 

Oxide  of  copper 

Mercury 

Oxide  of  silver 

Sulphurets 

Seleniurets 

Arseniurets 

Antimoniurets 

Tellurets 

Carburets 

Sulphuric  acid 

Nitric  acid 

Chlorides 

Bromides 

Iodides 

Fluorides 

Phosphates 

Cartonates 

Boracic  acid 

Hydrates 

Silicates 

Salts  of  metallic  acids 


It  has  only  come  within  our  province  to  describe  the  im- 
plements and  adjuncts  employed  in  blowpipe  analyses,  with 
some  few  examples  of  the  practical  results  obtained  by  means 
of  them.  The  excellent  manual  of  Griffin,  and  the  works 
upon  the  subject  by  Berzelius  and  Plattner,  contain  most 
complete  accounts  of  this  branch  of  manipulative  chemistry, 
and  of  the  mode  of  conducting  investigations  by  means  of  it. 


ANALYSIS  BY  POLARIZATION  OF  LIGHT. 


891 


CHAPTER   XXVIII. 

APPLICATION  OF  THE  CIRCULAR  POLARIZATION  OF  LIGHT  TO 
THE  ANALYSIS  OF  SACCHARINE  SUBSTANCES. 


When  a  ray  of  common  light  passes  through  a  doubly  re- 
fracting crystal,  such  as  a  rhomb  of  Iceland  spar,  it  is  sepa- 
rated into  two  rays  which  have  peculiar  properties  differing 
from  the  original  ray.  These  rays  are  found  to  possess  similar 
properties  in  planes  at  right  angles  to  each  other ;  that  is  if 
we  suppose  one  ray  to  have  certain  properties  in  a  horizontal 
plane,  the  other  ray  will  have  similar  in  a  vertical  plane. 
Each  of  these  rays  is  said  to  be  polarized,  and  to  have  its 
plane  of  polarization  at  a  right  angle  to  that  of  the  other. 

If  one  of  these  rays  be  absorbed  or  prevented  from  passing 
by  any  means,  and  the  other  whose  plane  of  polarization  we 
will  suppose  to  be  horizontal,  be  allowed  to  pass  through  an- 
other doubly  refracting  crystal,  as  Iceland  spar,  in  certain 
positions  the  polarized  ray  will  be  again  doubly  refracted, 
and  we  shall  see  two  images  of  the  object  from  which  the 
light  comes.  But  if  we  turn  the  second  crystal  in  such  a  posi- 
tion that  its  principal  section^  that  is  the  plane  passing 
through  the  axis  A  X,  (which  is  the  line 
joining  the  obtuse  summits  of  the  rhomb,) 
and  perpendicular  to  one  of  its  faces,  is 
vertical,  that  is  at  right  angles  to  the 
plane  of  polarization  of  the  ray,  only  one 
ray  will  pass  through  the  crystal,  the 
other  being  stopped,  and  but  one  image 
will  be  seen.  If  now  we  continue  to  turn 
the  second  crystal,  the  remaining  ray  de- 
creases in  intensity,  and  the  other  begins 
to  reappear,  and  if  we  go  on  turning  the 
crystal  through  90°,  the  first  ray  will  disappear  and  the  ray 
which  had  formerly  disappeared  will  be  at  its  maximum  in- 
tensity.   If  we  turn  the  crystal  through  another  90°,  this  ray 


Fiff.  362. 


% 

392  POLARIZER  AND  ANALYZER. 

will  again  disappear  and  the  other  reappear.  And  so  on 
these  changes  alternate  through  every  90°,  until  finally  we 
come  again  to  our  original  position,  with  the  principal  section 
at  right  angles  to  the  plane  of  polarization. 

Now  it  is  evident  that  if  we  should  stop  one  of  the  two  rays 
into  which  the  second  crystal  refracts  the  polarized  ray,  then 
in  certain  positions  we  should  have  no  light  transmitted,  and  in 
positions  at  right  angles  to  these,  we  should  have  the  greatest 
intensity. 

The  first  of  these  crystals  of  Iceland  spar  is  called  the 
polarizing  crystal,  or  polarizer,  and  the  second  the  analyzer. 
When  we  make  use  of  two  Nichols  prisms,  (which  are  rhombs 
of  Iceland  spar  so  contrived  as  to  transmit  only  one  of  the 
doubly  refracted  rays,)  one  as  the  polarizer,  and  the  other  as 
the  analyzer,  and  the  analyzer  is  turned  until  its  principal 
section  is  at  right  angles  to  the  plane  of  polarization  of  the 
polarized  ray,  no  light  passes.  This  position  is  called  the 
azimuth  zero.  When  the  analyzer  is  turned  through  90° 
from  this  position  the  polarized  ray  attains  its  greatest  bright- 
ness. Turning  again  90°,  the  light  disappears,  and  reappears 
on  turning  through  another  90°,  and  finally  again  disappears 
in  returning  to  the  azimuth  zero. 

If  when  the  polarizer  and  analyzer  are  in  this  position,  a 

piece  of  quartz  which  has  been  cut  from  a  crystal  at  right 

angles  to  its  axis  A  X,  or  a  solution  of  cane  sugar 

Fig.  363.     \,Q  placed  intervening,  so  that  the  polarized  light 

^        has  to  pass  through  them,  the  light  immediately 

R/K        reappears,  with  a  tone  of  color  depending  upon  the 

(j-V^  thickness  of  the  section  of  quartz,  or  solution  of 
°     cane  sugar.     If  we  turn  the  analyzer  in  a  direc- 

sItt!^  tion  from  left  to  right,  then  if  the  original  color 
j[  was  orange,  for  example,  we  shall  find  the  pris- 
matic colors  succeeding  each  other  in  the  order  of 
orange,  yellow,  green,  blue,  indigo,  violet,  red.  When  the 
colors  succeed  each  other  in  this  order,  the  quartz  and  the 
sugar  are  said  to  deviate  or  rotate  the  plane  of  polarization 
to  the  right.  When  by  turning  the  analyzer  in  the  same 
direction  the  colors  succeed  each  other  in  inverse  order,  or 
when  by  turning  the  analyzer  from  right  to  left  the  colors 
succeed  each  other  in  the  same  order,  the  quartz  and  the 
sugar  are  said  to  deviate  the  plane  of  polarization  to  the  left. 
In  the  former  case  the  quartz  and  sugar  are  said  to  be  right- 


CIRCULAR  POLARIZATION. 


393 


handed^  in  the  latter  left-handed.  Crystallizable  sugar  de- 
viates the  plane  of  polarization  always  to  the  right,  or  is 
right-handed,  uncrjstallizable  to  the  left  or  is  left-handed. 
Some  specimens  of  quartz  are  found  to  deviate  the  plane  of 
polarization  in  one  direction,  and  some  in  the  opposite. 

When  the  analyzer  is  not  a  Nichol's  prism,  but  only  an 
ordinary  doubly  refracting  prism,  which  allows  both  rays  to 
pass,  and  is  in  the  position  in  which  one  of  the  rays  into 
which  the  polarized  beam  is  refracted  is  stopped,  then  the 
plate  of  quartz  will  cause  it  to  re- 
appear, and  we  shall  have  the  two  F^s-  364. 
beams  o  and  e.  Fig.  364,  colored  but 
not  with  the  same  tint,  one  comple- 
mentary to  the  other.  Two  colors 
are  said  to  be  complementary  if  they 
produce  white  light  when  mixed. 

These  two  colors  vary  as  we  rotate  the  analyzer,  but  in  all 
cases  they  are  complementary. 

If  when  the  analyzer  is  at  the  azimuth  zero,  we  substitute 
for  the  simple  plate  of  quartz,  a  plate  composed  oi  right  and  left- 
handed  quartz,  R  and  L,  Fig.  365,  the 
line  of  separation  of  which  is  vertical,  ^ig-  365. 

then  as  they  are  of  the  same  thickness,  we 
shall  have  the  same  appearance  and  co- 
lors in  the  two  rays,  as  we  had  in  the 
case  of  the  simple  plate  of  quartz  of  the 
same  thickness.  For  the  two  kinds  of  quartz  being  of  the 
same  thickness,  the  one  deviates  the  plane  of  polarization  as 
much  to  the  right  as  the  other  to  the  left.  Hence  each  one  of 
the  rays,  although  of  complementary  colors,  will  be  of  the 
same  uniform  color  in  itself. 

But  if  the  analyzer  be  turned  each  beam  will  be  divided 
into  two  different  colors,  ?,  r,  and  Z,  /,  Fig.  366,  and  the  colors 
in  one  beam  will  be  complementary  to  the  colors  in  the  other 
beam. 

If  two  plates  of  quartz  of  equal  thickness,  one  right-handed, 


Fig.  366. 


Fig.  367. 


394  ventzke's  apparatus. 

the  other  left-handed,  be  made  to  overlap,  Fig.  367,  then  the 
effects  of  each  separately,  will  be  neutralized,  and  the  plane 
of  polarization  will  not  be  deviated  in  either  direction ;  and 
if  the  analyzer  be  at  the  azimuth  zero,  only  one  ray  will  pass, 
as  if  the  quartz  had  not  been  interposed. 

Having  now  prefaced  with  the  phenomena  of  polarized  light 
employed  in  chemical  analysis,  we  shall  describe  the  appa- 
ratus of  M.  Ventzke,  which  is  a  modification  of  the  original 
apparatus  of  M.  Biot,  who  first  discovered  the  property  of 
the  circular  polarization  of  light  possessed  by  sugars,  and 
other  organic  matters,  and  who  founded  on  this  discovery 
his  process  of  analyzing  solutions  of  saccharine  substances. 
This  apparatus  was  used  by  Prof.  McCulloch  in  quite  an  ex- 
tended series  of  analyses  for  the  government  of  the  United 
States.* 

A  sketch  of  the  apparatus  is  given  in  the  annexed  cut.    The 

Fig.  368.  Fig.  369. 


analyzer,  which  is  a  Nichol's  prism,  is  placed  in  a  brass  socket 
at  A,  another  view  of  which  is  given  at  A  (Fig.  369).  This 
socket  is  capable  of  a  motion  in  the  graduated  disk  and  car- 
ries an  index  I,  which  moves  over  the  disk  and  measures  the 
number  of  degrees  from  the  zero  point,  through  which  the 
analyzer  is  moved.  It  is  turned  by  means  of  a  small  disk  F, 
called  the  pinion  disk,  which  carries  a  pinion  wheel  gearing 
into  a  larger  toothed  wheel  attached  to  the  analyzer. 

The  polarizer,  which  is  also  a  Nichol's  prism,  is  fixed  in  a 
brass  socket  at  B.     This  socket  has  a  toothed  wheel  which 

*  Senate  Document  165,  2Sth  Congress,  2cl  Session. 


ventzke's  apparatus. 


395 


gears  into  the  threads  of  a  perpetual  screw,  which  is  moved 
by  a  milled  head  at  h.  The  whole  socket  is  capable  of  motion 
in  a  groove,  and  of  being  fixed  in  any  position  by  the  binding 
screw  d.  The  tube  which  is  to  contain  the  solution  of  sugar 
is  shown  at  D.  The  peculiar  construction  of  this  tube  will 
be  explained  directly.  A  lamp  is  placed  at  E,  which  is  re- 
commended to  be  used  instead  of  the  sun,  in  order  to  insure 
a  uniform  intensity  of  light.  The  whole  instrument  is  mounted 
on  an  iron  foot. 

The  only  adjustment  necessary  is  to  bring  the  principal 
section  of  the  analyzing  prism  at  right  angles  to  the  plane  of 
polarization  of  the  polarizer.  This  is  done  by  putting  the 
index  of  the  analyzer  at  zero,  on  the  graduated  arc,  and  then, 
by  means  of  the  screw  6,  turning  the  polarizer  until  we  have 
obtained  the  point  of  greatest  darkness.  This  adjustment  is 
best  made  by  sun  light.     This  gives  the  azimuth  zero. 

It  has  already  been  mentioned,  that  crystallizable  sugar 
deviates  the  plane  of  polarization  to  the  right,  and  uncrystal- 
lizable  to  the  left.  Now,  as  the  sugars,  which  in  the  majority 
of  cases  the  chemist  is  required  to  analyze,  contain  the  two 
kinds,  it  becomes  necessary  to  appreciate  the 
effect  of  each  kind  separately  in  deviating  the 
plane  of  polarization.  It  has  been  found  that 
when  hydrochloric  or  sulphuric  acid  is  added  to 


a  solution  of  pure  cane  sugar,  which  always 
polarizes  to  the  right,  and  the  mixture  is  suf- 
fered to  stand  for  10  or  12  hours,  or  is  gently 
heated,  the  cane  sugar  is  converted  into  the 
uncrystallizable,  which  deviates  to  the  left,  or 
is  left  handed.  Advantage  is  taken  of  this  fact 
in  M.  Biot's  process  of  analysis.  A  solution  is 
made  which  contains  25  or  50  per  cent,  of  the 
sugar  to  be  analyzed.  This  solution  is  then 
filtered,  and  if  it  is  much  colored  it  is  deco- 
lorized by  passing  it  through  a  tolerably  coarse 
bone  black.  It  is  then  placed  in  a  glass  tube  a, 
Fig.  370,  the  ends  of  which  are  ground,  and  are 
fitted  with  screws  as  shown  in  the  figure.  Over 
the  end  of  the  tube  is  placed  a  round  disk  of 
glass,  6,  with  parallel  surfaces,  and  then  the  cap  c  is  screwed 
down  over  this  so  as  to  hold  it  tightly  in  its  place.     A  hole  is 


396  METHOD  OF  ANALYZING  SUGARS. 

pierced  througli  the  cap  at  d,  which  allows  the  light  to  pass. 
The  other  end  of  the  tube  is  provided  with  a  similar  arrange- 
ment. This  tube  having  been  filled  with  the  solution  is  placed 
in  the  apparatus  in  the  position  shown  at  D.  The  analyzer 
is  then  turned  to  the  right  until  the  bluish  violet  ray  begins 
to  appear.  This  color  is  chosen  because  it  is  one  of  the  most 
delicate,  and  its  amplitude  is  small,  and  therefore  is  observed 
with  the  greatest  certainty.  This  angle  is  noted.  Then  one 
part  by  volume  of  hydrochloric  acid  is  added  to  nine  parts  by 
volume  of  the  solution,  so  that  the  original  sugar  solution 
becomes  -^^  of  the  acidulated  solution.  This  is  then  suffered 
to  stand  for  10  or  12  hours,  or  if  gently  heated  to  154°  Fahr., 
is  entirely  converted  into  uncrystallizable  sugar  in  15  or  20 
minutes.  It  is  again  placed  in  a  tube,  and  the  analyzer  turned 
to  the  left  until  the  same  bluish  violet  tint  appears.  This 
angle  is  then  noted.  Previously  to  adding  the  acid,  the  dens- 
ity of  the  solution  is  observed  either  by  a  good  hydrometer, 
or  by  weighing. 

Calling  the  angle  observed  before  acidulation  the  direct 
angle,  the  angle  observed  after  acidulation  the  inverted  angle, 
and  the  ratio  of  the  original  solution  to  the  acidulated  mix- 
ture, which  in  the  above  example  is  y^^,  the  ratio  of  dilution; 
then  for  convenience  we  may  take  the  notation. 

a  =  direct  angle, 

a"  =  inverted  angle, 

n  =  ratio  of  dilution  =  0.9, 

d  =  density  of  the  solution, 

e    =  per  cent,  of  the  original  sugar  contained  in  the 
solution,  which  is  either  25  or  50, 

X  =  the  per  cent,  of  pure  cane  sugar  in  the  original 
sugar. 
Knowing  the  first  five  quantities,  we  may  calculate  the  last 
by  the  following  rule:* 

*  The  formula  which  Mr.  M'Culloch  has  given  at  p.  24  of  his  Second  Report, 
Senate  Doc,  No.  209,  29th  Congress,  2d  Session,  is 


153.7G  ned 
in  which 


1  _L  //  fi'f 

— — —  a'  in  which  a'  =z  n  a,  and  r"  = — , 

1.38  a' 


the  same  notation  as  given  above. 


DECOLORIZATION  OF  COLORED  SOLUTIONS.  397 

Multiply  a  by  w,  with  the  product  thus  obtained,  as  a 
divisor,  divide  a" :  add  1  to  the  quotient,  and  multiply  by  the 
product  of  a  and  n ;  divide  the  product  thus  obtained  by  1.38: 
divide  the  quotient  by  153.76  multiplied  by  ti,  by  e  and  by  x\ 
the  quotient  will  give  the  value  of  x,  or  the  per  cent,  of  pure 
crystallizable  cane  sugar,  contained  in  the  original  sugar. 

In  analyzing  molasses  the  same  process  is  followed.  The 
only  difficulty  which  occurs  is  the  decolorization  of  the  solu- 
tion; which  maybe  done  by  repeatedly  filtering  through  tubes 
filled  with  coarse  bone  black.  A  glass  tube  of  J  or  f  inch 
interior  diameter,  and  about  2  or  3  feet  long,  is  taken,  which 
is  narrowed  at  one  end  by  the  lamp  and  blowpipe;  a  loose 
plug  of  paper  is  then  put  in  the  tube  near  this  end,  and  the 
tube  is  filled  with  coarse  bone  black.  It  is  recommended  by 
M.  Clerget  not  to  collect  the  first  part  of  the  filtrate,  as  the 
bone  black  absorbs  some  sugar  as  well  as  coloring  matter,  and 
thus  alters  the  per  cent,  of  the  solution.  He  recommends 
that  a  volume  of  the  solution  about  equal  to  that  of  the  bone 
black  should  be  lost.  The  liquor,  if  not  sufficiently  decolor- 
ized by  the  first  filtration,  may  be  passed  through  the  same 
black  again. 

Other  processes  may  be  employed  which  are  known  to 
chemists,  such  as  precipitating  the  extractive  and  coloring 
matters  by  the  subacetate  of  lead.  In  this  case  the  solution 
of  the  subacetate  should  be  used  as  pure  water,  in  making  the 
original  solution.  In  defecating  cane  juice  M.  Clerget  pro- 
ceeds as  follows:  He  prepares  a  solution  of  isinglass  (fish- 
glue)  by  macerating  5  or  6  grammes  of  it  in  250  grammes  of 
cold  water  during  3  hours.  He  thus  obtains  a  paste,  which 
is  sifted  or  strained  through  a  piece  of  coarse  linen,  and  mixed 
with  100  grammes  of  white  wine  or  alcohol  diluted  with  water. 
Thus  is  obtained  a  gelatinous  mass  which  may  be  diluted 
with  water  until  its  volume  is  1  litre  (61  cubic  inches).  This 
will  keep  in  a  corked  bottle  from  15  to  20  days,  according  to 
the  temperature.  It  should  not  be  used  when  it  becomes  very 
sour.  If  a  small  quantity  of  this  be  added  to  cane  juice,  or 
any  solution  of  sugar  and  mixed  with  it  and  then  the  same 
volume  of  alcohol  be  added,  the  whole  is  coagulated,  and  the 
solution  is  left  perfectly  clarified.  The  dilution  of  the  solu- 
tion which  thus  takes  place  must  be  taken  into  account  in  the 
calculation  of  the  per  cent,  of  sugar  dissolved.     It  may  be 


398  soleil's  saccharimeter. 

compensated  by  increasing  the  length  of  the  tube  in  the  same 
ratio. 

In  the  October  number  of  the  Bulletin  de  la  Societe  d' en- 
couragement pour  V Industrie  JSfationale,  1846,  M.  Soleil,  the 
celebrated  optician  of  Paris,  has  described  a  nouveau  sac- 
charimetre  of  his  invention,  which  is  a  great  improvement  over 
the  instrument  which  has  been  described,  enabling  the  mea- 
surements to  be  made  with  great  precision.  The  instrument 
is  represented  in  the  cut,  Fig.  371. 

The  polarizer  is  placed  at  d,  which  is  either  a  Nichol's 
prisfn,  or  an  ordinary  doubly  refracting  prism.  The  ana- 
lyzer is  at  a,  which  is  a  doubly  refracting  prism,  which  sepa- 
rates the  polarized  beam  into  two,  and  in  certain  positions, 
allows  only  one  to  pass.  Immediately  behind  the  polarizer  at 
e,  two  pieces  of  quartz  of  equal  thicknesses,  one  right-handed, 
the  other  left-handed,  are  placed,  so  that  the  line  of  separa- 
tion is  vertical,  and  in  the  middle  of  the  field  of  view,  so  that 
one  acts  on  one-half  the  beam,  the  other  on  the  other  half. 
Now,  the  analyzer  being  at  the  azimuth  zero,  from  what  has 
been  said,  the  same  tone  of  color  will  be  produced  by  each, 
because  they  rotate  the  plane  of  polarization  equally  and  in 
opposite  directions.  Hence,  although  the  two  beams  into 
which  the  analyzer  will  separate  the  polarized  light  will  be  of 
complementary  colors,  yet  the  color  of  each  beam  will  be 
uniform  throughout.  Now  when  the  sugar  solution  is  placed 
at  71,  if  it  is  crystallizable  sugar  it  will  be  like  increasing  the 
thickness  of  the  right-handed,  and  diminishing  that  of  the 
left-handed  quartz ;  if  uncrystallizable,  like  increasing  the 
thickness  of  the  left-handed  and  diminishing  that  of  the  right- 
handed  quartz.  Hence,  in  either  case  the  plane  of  polariza- 
tion will  be  rotated  more  in  one  way  than  in  the  opposite, 
and  the  amount  of  this  rotation  will  depend  upon  the  number 
of  particles  of  sugar,  that  is  upon  the  per  cent,  of  the  solution, 
and  the  length  of  the  tube;  and,  therefore,  each  of  the  two 
beams  will  be  no  longer  of  the  same  uniform  tint,  but  one-half 
of  one  beam  will  be  of  one  color  and  the  other  half  of  the 
other  color,  and  the  other  beam  will  also  have  two  colors 
complementary  to  those  of  the  first. 

In  order  to  measure  the  degree  to  which  the  plane  of  polar- 
ization is  rotated  in  either  direction,  M.  Soleil  ascertains  the 
thickness  of  the  quartz  of  either  kind,  which  is  necessary  to 
compensate  the  effect  of  the  sugar  that  is  to  render  each  beam 


SOLEIL  S  SACCHARIMETER. 


399 


v<^ 


400 


SOLEIL'S  SACCHAIIIMETER. 


of  a  uniform  tone  of  color.     This  is  accomplished  by  his  com- 
pensator,  which  part  of  the  apparatus  is  placed  at  c. 

Now  the  effect  of  the  sugar  in  deviating  the  plane  of 
polarization  depends  upon  its  purity  and  upon  the  strength 
of  the  solution ;  therefore,  in  order  to  compensate  the  effect 
of  the  sugar  in  every  case,  it  would  be  necessary  to  have  a 
number  of  pieces  of  quartz  of  various  thicknesses,  and  of 
contrary  effect  to  the  sugar,  in  deviating  the  plane  of  polari- 
zation.    This  would  be  inconvenient,  and  M.  Soleil  overcomes 

Fig.  372. 


the  difficulty  in  his  compensator.  Immediately  before  the  sugar 
solution,  and  near  c,  is  placed  a  piece  of  quartz,  which  rotates 
the  plane  of  polarization  to  the  right.  At  c  there  are  two 
pieces  of  left-handed  quartz,  cut  as  shown  in  Fig.  372.    Now 

Fig.  373. 


,  soleil's  saccharimeter.  401 

when  these  two  pieces  a  and  h  are  in  the  position  shown  in  the 
figure,  they  have  together  the  same  thickness  as  R,  and  being 
of  an  opposite  kind  to  R,  of  course  they  neutralize  its  effect. 
But  when  they  are  in  the  position  shown  at  c?  c?  (Fig.  373),  then 
their  thickness  in  the  direction  of  the  ray  I  I,  is  less  than  the 
thickness  of  R^  and,  therefore,  the  effect  of  R  will  predominate, 
and  it  will  compensate  for  a  left-handed  (uncrystallizahle) 
sugar.  When,  however,  the  pieces  are  in  the  position  shown 
at  e  and  /,  then  the  thickness  through  ^  ?  is  greater  than  that 
of  R,  and  their  deviation  will  predominate,  and  will  compensate 
for  a  right-handed  (crystallizable)  sugar. 

These  two  pieces  are  mounted  upon  a  small  rack  work  into 
which  gears  a  pinion,  which  moves  them  in  opposite  direc- 
tions. The  pinion  is  turned  by  a  milled  head  at  b.  These 
two  pieces  have  likewise  attached  to  them  two  scales,  which 
are  represented  at  c  d .  The  smaller  scale  serves  as  a  vernier, 
10  of  whose  divisions  correspond  to  9  on  the  larger  scale. 
They  are  each  graduated  in  opposite  directions  from  a  com- 
mon zero  point,  and  the  extremities  of  both  scale  and  vernier 
are  marked  D,  droits  right,  and  G,  gauche,  left.  When  the 
zero  points  coincide,  the  two  pieces  are  in  the  position  shown 
at  a  and  6,  and  have  the  same  thickness  taken  together,  as  R. 

Each  division  of  the  large  scale  counts  10,  and  each  of  the 
small  scale  1.  Thus  if  the  zero  point  of  the  vernier  was  be- 
tween 4  and  5  on  the  large  scale,  very  near  5,  we  glance 
along  the  vernier,  until  we  find  a  division  which  coincides 
with  a  division  on  the  large  scale.  If  this  division  is  9,  then 
the  instrument  gives  the  reading  40  on  this  large  scale,  and 
9  on  the  vernier,  or  49. 

A  lens  is  placed  at  g,  which  is  to  be  so  adjusted  as  to  see 
clearly  the  vertical  division  line  of  the  two  quartz  placed  at  e. 
This  adjustment  should  be  made  while  the  tube  u  is  full  of 
water.  A  spiral  spring  is  placed  at  q  to  press  against  the 
tube  w,  and  keep  it  in  its  place.  The  whole  instrument  is 
mounted  on  a  pillar  and  foot. 

Now  supposing  the  lens  at  g  adjusted  so  as  clearly  to  see 
the  line  of  separation  of  the  two  pieces  of  quartz  at  e,  and  the 
scale  and  vernier  adjusted  to  their  common  zero  point,  the 
only  remaining  adjustment  is  that  of  the  analyzer  to  the 
azimuth  zero,  which  may  be  done  by  rotating  it  in  its  socket 
until  one  of  the  images  of  the  aperture  at  o  has  a  uniform 
violet  color.  When  this  is  done,  the  analyzer  is  fixed  firmly 
in  its  place  by  means  of  the  binding  screw  p. 


402  clekget's  method. 

In  this  apparatus  a  tube  of  the  solution  is  used  as  in  the 
former  case,  and  in  order  to  determine  the  amount  to  which 
it  deviates  the  plane  of  polarization,  the  button  at  h  is  turned 
in  whatever  direction  tends  to  produce  a  uniform  violet  color 
in  the  colored  ray  which  was  uniformly  violet  before  the  solu- 
tion was  placed  in  the  apparatus.  Then  the  direction  in 
which  the  vernier  has  moved  will  determine  the  kind  of  de- 
viation :  if  towards  D  the  plane  of  polarization  is  rotated 
towards  the  right ;  if  towards  G,  to  the  left. 

Analyses  may  be  made  in  precisely  the  same  way,  and 
calculated  by  the  same  formula  with  the  exception  of  the 
numerical  factor  153.76,  which  will  have  to  be  determined 
anew,  as  it  depends  on  the  instrument. 

M.  Clerget  has  given  a  table  which  supersedes  the  neces- 
sity of  calculation.*  His  process  of  analysis  is  as  follows  : — 
Having  made  a  solution  containing  16.471  per  cent,  of  pure 
dry  cane  sugar,  and  placed  it  in  a  tube  20  centimetres 
(7.8  inches)  long,  he  found  that  it  deviated  the  plane  of  po- 
larization to  the  right  100°.  Now  if  we  were  analyzing  a 
sugar  known  not  to  contain  any  left  polarizing  substance, 
and  we  should  find  that  it  deviated  the  plane  of  polarization 
80°  to  the  right,  then  by  stating  the  proportion : 

100  :  16.471  :  :  80  :  X  =  13.177. 

Now  dividing  13.177  by  16.471,  we  get  the  per  cent, 
of  pure  cane  sugar  in  the  original  sugar.  If,  instead  of 
making  this  calculation,  we  refer  to  the  table  at  the  end  of 
this  article,  and  look  down  the  column  A  to  the  number  80, 
the  number  in  column  B  on  the  same  horizontal  line,  is  the 
number  of  grammes  and  centigrammes  contained  in  a  litre 
of  the  solution.  The  solution  is  supposed  to  be  observed 
through  a  tube  of  a  constant  length,  20  centimetres. 

As  the  sugars  to  be  analyzed  generally  contain  left  polariz- 
ing sugar,  it  is  necessary  to  take  into  consideration  the  effect 
of  this  substance.  A  solution  of  the  sugar  or  molasses  is 
made  of  the  normal  per  cent.  16.471,  and  decolorized  and 
clarified  according  to  the  methods  described.  A  tube  20  cen- 
timetres long  of  the  solution  is  then  placed  in  the  instrument 
and  the  direct  deviation  noted.  Ten  volumes  of  the  solution  are 
then  added  to  one  volume  of  concentrated  hydrochloric  acid, 

*  Bulletin  cle  la  Societe  d'encourageraent  pour  I'lndustrie  Nationale,  Oct.  184G. 


clerget's  method. 


403 


and  then  put  into  a  convenient  vessel  (a  matras  is  best  adapted 
to  this  purpose),  and  the  whole  placed  in  a  water  bath  and 
brought  up  to  the  temperature  68°  cent.  (154°  Fahr.).  The 
heat  is  so  regulated  as  to  require  about  fifteen  minutes  to 
bring  it  to  this  temperature.  It  is  then  placed  in  a  vessel  of 
cold  water,  in  order  to  bring  it  to  the  temperature  of  the  sur- 
rounding air,  and  afterwards  in  a  tube,  represented  in  Fig. 
374,  adapted  with  a  thermometer,  so  as  to  take  the  tempe- 

Fig.  374. 


rature  of  the  liquor  at  the  time  the  inverted  angle  is  observed 
in  the  polarizing  instrument ;  M.  Clerget  having  found  that 
the  temperature,  at  which  the  observation  is  made,  has  a  great 
influence  on  the  deviation  of  the  plane  of  polarization.  Hav- 
ing increased  this  last  number  by  y^oth  in  order  to  compensate 
for  the  dilution  by  the  acid,  it  is  added  to  the  direct  deviation, 
and  then  entering  the  table,  at  the  temperature  at  which  the 
inverted  deviation  was  noted,  we  find  the  number  nearest  to 
the  sum,  and  the  number  in  the  column  A  on  the  same  hori- 
zontal line,  will  give  the  per  cent,  of  pure  sugar. 

In  the  case,  where  the  deviation  before  the  acidulation  and 
after,  takes  place  in  the  same  direction,  which  may  happen  if 
the  crystallizable  sugar  is  mixed  with  a  large  quantity  of  un- 
crystallizable,  then  the  difi'erence  instead  of  the  sum  of  the 
deviations  is  to  be  taken. 

Examples. — Suppose  a  liquor  before  acidulation  gives 

a  direct  deviation  of 75° 

and  after  acidulation,  an  inverted  deviation  at  the  tem- 
perature of  15°  cent. 20° 


Sum 


95° 


404  clerget's  method. 

Entering  the  table  at  the  column  of  15°  centigrade,  we 
find  95.5  corresponds  to  70  per  cent,  of  cane  sugar. 

Again,  suppose  before  acidulation  the  direct  deviation 
is  -        -        -        -        -        .        .        .        -         80° 

and  after  at  20°  cent,  the  direct  deviation  is    -        -         26° 

Difference     -----        54° 
In  the  column  20°  cent.,  53.6  gives  40  per  cent,  cane  sugar. 

Those  who  wish  to  understand  fully  the  application  of  the 
phenomena  of  circular  polarization  to  chemical  analysis,  are 
referred  to  the  memoirs  of  M.  Biot  in  xiii.  xiv.  xv.  vols, 
of  the  Memoir es  de  VAcadSmie;  to  Professor  McCuUoch's 
Keport,  Senate  Documents,  No.  165,  28th  Congress,  second 
session,  or  the  Scientific  Memoirs,  vol.  iv.  p.  292,  which  con- 
tains a  translation  of  some  of  M.  Biot's  papers. 


ANALYTICAL  TABLES. 


405 


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ANALYTICAL  TABLES. 


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I—,  tq 
I  d  --^ 

'inm 


JO  i  IQ  C-.  , 

COT  ind  ( 
in  in  in  in ' 


iSco 


-rf  in  00  ( 

1  CO  i>-  t>-  ( 


COt^CiO  — « 


I  q  CO  q  q  -»  !>;  — 

.  t-  00  00  JO  JO  S  00 


1    5^ffl    ! 


;  q  •>r  JO  . 
>  in  in  in  I 


.  in  X  CO  : 

;  X  d  -^  ; 
I  in  in  CO  c 


icoqq- 
>  in  d  00  ( 

I  CO  CO  CO  c 


©coco 


O  TO)  — 


50  q  q  CO  t>;  -: 

inoininin®S«5cocD 


inoi  50 

'  d  tx 

CO  c 


CO  ceo 

d-^  50 
CO<^i> 


>i  t-  J^  t^  t- 


t^^rp  XCO 

CO  ind  t>^d 

J>.  !>.  t^  !>.  t^ 


in  C5  CO  CO  c  Tp  i~.~ 


Tp  rp  T  T  o  m 


rr  JL;  50  in 

Ss  in  >n  in 


C  CO  CO  t 

x'  d  —  c 

in  CO  CO  < 


'  a:-  —  in 
!  in  i>^  i' 

)  *^coco 


Oi  50CO 
d  —  50 
CO  t^t^ 


q  CO  t>;  —  in 
rp  in  d  00  d 
i^  *^  t^  1^  i^ 


00  50  q  q  CO  !>;  q 


in  CO  00  T  c 


q  ^-J  c 
d  50 « 
in  in  I 


;  "^  '^.  ^  ■ 

I  in  S  CO  : 


:  O  TP  1^   . 
i  ^  J^  X  I 


I  50  as  o  T  1^ 
It  in  i^  odd 

.!>.<>■  t^  t^  t>. 


I  in  in  in  in  in 


CO  t»  —  1 

'  d  5J( 

coco  ! 


•  inojco  t^O" 


I  rp  in  {>•  'X  C  1 
.  i^  t^  t^  t^  00  I 


t-i  in  c:  50  in  o  T 


X  50COO5COt^ 


STX  50 

«  ujinin 


in  ocoi 
dd50( 
in  CO  CO! 


;  in  q  50  ( 

:  CO  coco  i 


I  X  5J  CO  =  to 

I T  d  *■-  d  d 

if*  <>.<>■  t>.  00 


t>;  —  in  q  50  q  q 

00  X  SJ  (X  JO  X  o 


I  €^    '-    =   • 
iTTin> 


50  q  q  T  : 

I  in  in  in  iri  I 


>COCOCOOCOCCCCf»t* 


ANALYTICAL  TABLES. 


407 


'opq 


«5aqo«waqT-^woo5»-t■^^*oc^«o^».  pcowaDOC5cpo5i-<'*oo5WTj;i>.< 


S§S^ 


i^S^o*  —  ^ 


g8S5iSg§S§§SS&g2::2S222i:22S?;?J^ 


't^OOl^  00, 


'     "      '      ■>  CD  05  O  C 

lOOlOC 


»qxoe3oci'r«Trr«o«ooo^-iti<i^oo»ioa)^'«>cosiC<>oQDoco!005'?*'9< 


«5jq— ;eo«C3i^Oja 


^  C5  »  Ci  0»  LT  X    r^  'S"  t>-  _   Sy  lO    ^   r-;  TT  t^ 


^SIwS 


oqTHrt<t>.oeo«oo30J«5ao»-iTj<jt^occicoo5«icx^rri^scc-.cci5\i 


C5  C^  l«  Cl 


^rj«QD^^t^OTJ>l>.pS^«>0«OS5WcOO;OJ«3X'7l«Oa0^^aO  — 
>JOQDXIC5CiOi050505C5^0S=_Oi  =  —  —  r-(-^  — —  «OJW(MS« 


i§li 


<g;  j^  -,  rr  i^  _  rr  i>.  ^  ,3-  l>.  ;^  .0  1,.  ^  ,;>  O  O  CO  «  w.  CC.  »  33  'M  O  iT^  O*  vfS 

XX05C5C5S503050iS5  0  0SCOS=-^-^-H-^-^rt-^  —  ■MWMC^ 


C3  3^  O  vfc; 

lo  t>^  od  oj 

0»  <N  5^  5< 


X  r^  TJ<  j^    _  TT  ^   _  . 

ua  xocjcjo; 


■  r-  TT  t^  O  -"T  i--  ^ 


(^  3  ^  t^  O  ! 


iSoJcyco 


•  rj"  j^  —  lO  J. 


1  w  5>*  CO  ■ 


X  c*  w  cc 


;cB»-j«5QD-^ioxwi«Qoc^icosc^»no5Wp050^-qqco®C;  copo 
Joi^c^foirsdi>^oid»-Jco'3"u:>r»>-ci  —  '?ico»odt^ojd-jco^d 


COO  p  eo 
r^  x  s  -H 


CO  aid  Oi  a  i 


»J  lO  Ci  -w  o 


Tji  ffl  j>;  »■ 


:?  o  —  CO  t^  w  -^j"  t^  =  -^r  1^  r-  -"T 
d  --  CO  •^  m'  *^  -o  C3  —  rj  CO  lo  d 


X  T—  lO  X 

cnScoco 


I  ■<j>  X  —  lO  JU  C^  1 


1  CO  -o  ;=  CO 
j  ^  S5  X  oi 


t>-  O  t  <>•  —  rr  X  ^  «5  X  W  lO  Oi 

2  2J:tZ2ifi'S?3?iS55^ 


•«*  X  —  lO  od; 


i  S3  coo  p  CO 

'  X  d  —  CO  •» 


i-^  TV  CO  vrj  ! 
03  03  03  03  ; 


■SiiiS 


^_  TT  X  --  lO 

C3  03  &  03  03 
~^"35««0O5 

d-ieo^  in 

03  03  03  03  03 


acoi 

503; 
CO^Oi 
03  03 


'SSS2: 


>opco 

icoSeo 


iCOt^O"*^"  —  OX'N0  03eOI>.O^TQD 


O  't  t^  »-i  lO 


p  :v  p  p 
•r-'  (t5  d  -- 


^  — -iiiiH--?}?}! 


)  — >o  pco 
IcocowS 


t^  ^<oai  7i 


<o  o 


5SSSS' 


oo- 

■i2: 


'  <--  —  lO  03  CM  O  S  TJ"  t^  -    >fj  s:   .M 

;2J^^22i2c5?Js5o3^?5^ 


P  P  TT  t^. 

^  CO  CO  CO 


r^  vq  X  »J  -i..  • 

5&d3  03  03< 

«»•  CD  (N  «;  d' 
a»03ao>o 


I  <>.  _  lo  03  CO 


S82:: 


S^  «5  p  CO  !>;  —  ^.  J-.  -^  -   p  .J  i~: 

co^ior-^ccdT-IjiTror-'ood 


iSS^ 


CO  r^  -<  u5  03  CO  a: 


;S5SSS8S§: 


:2J:2g=3S55^£;2J5 


;S^S 


!>.  —irtpCOl 
Ob  Ob  Ca  C6  Oa  < 


'  lo  C3  n  o  o  ■ 


iO'^X—  OC3C0<>.  —  "COSCOi^ 


i.  rr  J.  w 


408 


ANALYTICAL  TABLES. 


^|M 

^|<1       §§|||SS||g|2^^25^|52S|^gJ|S^S^?i§| 

1 

O          1         i^C5e<?«OQD^e«5«C5?<"»t-0'?<iOGC;0«ttCS«rpt>.050JOt^O«<»aD-^ 

1 

g 

o 

CO 

t-  ;;  r:  -^  X  —  TT  t-  o  ■?!  ir:  7.  —  TT  :c  cr.  T<  o  a;  o  CO  ts  C5  -w*  t^  o  cc  !C  X'  —  -"s- 

i=    /■  ~  d  —  ?t  rr  i.~"  (-'  t"  Cv'  C:  TJ  r~  —  1.0  f^  x'  S;  —  fj  CO  -f  ®'  »^  x'  O  -^  Ct  CO  lO  O 

c5T>?irocor-rccor-r'?:Tr'^-r-rrrrr'r-*o>oioiq55ioioO'0«ooo 

o 

CO 

01  o  /  -  70  -  zr.  0*  uo  /-  -  CO  -.::  r.  o»  o  x  -  co  -.o  cs  o»  .o  x  c=  co  «;  c-.  O'J  o  x  = 

o              J.  s  rr  -,c  a  c^  -^  *^  =  r: :::  cr-.  7'  o  J.  -:  r:  !c  =5  c>»  iq  X  -^  rr  <>;  q  w  lo  JJ  -:  -r  «>: 

S 

OJ  o  X  -  -^  i^      CO  -i  c:  -.  TT  t^.  q  q  q  q  o^  uo  x  -  -r  <-  q  q  q  q  o<  >q  /.  _  q 

<5 

■  u               i-  =5  X  «;  ^.  S)  «  J-  -  T  .-  =  .-0  -i  5;  c^  o  J.,  r-.  TT  t-  q  «  q  q  c^.  o  a  ^  rr  t-  q 

1 

o 
o 

CM 

C<  o  X  —  rr  I-  =  75  -.c  C5  Oi  o  X  <M  >c  X  —  IT  t-:  q  q  q  q  0^  o  /.  -  ^r  <-  q  q  q 

t^  o  CO  :s  35  wo  C5  c><  in  X  —  T  1-  o  00  «  =:  00  «;  C5  (M  in  X  -^  •«'  t-.  —  -^  «>;  q  q 

w  in  X  -  rr  X  —  rr  1^  =  CO  -^  =  CO  tt  C-.  oi  in  X  ■?;  iq  X  —  r);  t-  -  -"t  1-:  q  q  q  q 

> 

O 
CJ 

i-  s  CO  -^  ~  CO  a  -.  01  -4;  05  TJ  o  X  0)  m  x  —  -q-  x  —  t  j^  o  "V  t^  o  q  cc  o  co  o 

< 

?, 
w 

(N  in  X  ^  m  X  —  in  X  -  ■»  t-  —  ^  j^  s  •»  t-_  q  q  !>.  q  q  q  q  q  q  q  q  q  q  oi 

o 

i^  o  CO  f-  =  00  •>=  -  q  w  q  q  q  q  q  q  q  q  q  q  q  q  q  q  q  ~.  ~>.  ~.  --. '».  q  ^. 

5 

o 

(ji in  »)  c^  in  X  oiin  x  oi  uo  x  o>*  m  x  •?* m  sr.  o*  c:  c;  o*  'O  ci  »i m  o  w o  o  o*  m 

o 

CM 

1-  =  CO  t-  =  ■*  *-  =  's-  '^  -  -v^  -  ''•  '  -^  -^  c:  -  q  X  —  q  X  (?j  iq  X  'N  q  q  OJ 

^ 

o        ,      ^  lo  X  -M  in  OS  cv)  o  05  r?  q  q  «  q  q  r:  t>;  q  'i;  t>:  _  ^  f-  -:  t  X  ^  iq  a  ?>  in  x 

2    1    igi^S§^^§^|^f|.^.3il^.l|-£-^S'lli|3iHi:S 

> 

o        1       CO  =  r;  t-  =  ■*  «-  -  '-'3  7-  —  «  X  -?!  vn  q  -7*  q  q  r;  q  _  cc  t-  q  ^r  <-  —  rr  x  --  o 

2   1    g§i^ii5^^1rii5?§§i2Slsiilil§SSi:S 

» 

H 

o 

^  m  X  oi  o  C-.  CO  «5  =  CO  t-  =  -o"  X  —  o  X  oj  q  q  -ri  -c  C5  q  t^  o  -a- 1^  —  •*  X  — 

o 

O                «£  q  -^  t^  -;  ^  X  c;  iO  q  ?»  q  _  ^. «-  _  -r  /,  q  o  x  ?;  q  q  q  q  q  ^  <•-  -  tt  >; 

3 

Q 

O                 -  O  cr.  7»  -i  _.  ~.  ,^  _  ^  X  -  >n  q  7.  q  =  ^  '-  -  -t  '.  '?  >-?  =^:  ~.  ==.  =.  =^  '-  -  '^ 

o        1       cs  c  -v  t-  -  o  X  OJ  q  q  -x  f>;  -  -^  X  5^  iq  q  q  i-  =  -r  x  -_  .q  q  r;  q  q  -r  J-  -< 

-   1    ^^ii^^zzlzl§2«2i'i^|-£iEEsiliHSi:i':!S 

o               o  o  TT  X  —  o  Ci  rt  i^  =  -^  X  S'j  -^  s:  c^  f ■  o  x  5)  :s  s  tt  t^  ^  o  C"  ^^  tt  o  ti< 

o               -  .o  ::r.  r:  -^  =  -T  A  'M  ^  =  c?'  i^  -  >c  Ci  to  c=  o  •*  X  Ti  «;  o  CT  !■»  -  lo  cr  CT^  i^  o 

1 

:o  =  -^  X  o>  CO  ci  CO  r — ^  in  05  CO  J- — ^  m  x  ci  co  =  •*  xj  ci  co  o  -v  t^  —  m  oi  co  j^ 

ELECTRICITY.  409 


CHAPTER   XXX. 

ELECTRICITY. 

Since  the  introduction  and  improvement  of  the  many  forms 
of  apparatus  now  in  use  for  the  production  of  electricity  and 
its  kindred  imponderables,  it  has  become  necessary  for  the 
chemist  to  be  well  acquainted  with  their  mode  of  manufacture 
and  employment.  Many  of  the  processes  of  the  laboratory 
are  now  performed  or  assisted  by  means  of  them,  and  a  know- 
ledge of  their  construction  is  important  not  only  as  being  the 
first  step  to  an  acquaintance  with  the  principles  concerned  in 
their  action,  but  also  as  affording  the  power  of  excelling  in 
practical  skill,  and  of  preparing,  extemporaneously,  instru- 
ments to  take  the  place  of  the  more  expensive  ones  made  in 
the  shops. 

We  propose  accordingly  to  give  an  account  of  the  mode  of 
operation  of  the  various  instruments  used  for  the  production 
and  detection  of  electricity,  with  directions  for  their  proper 
employment,  and  some  of  their  most  common  applications  to 
the  purposes  of  the  experimenter  and  practical  chemist,  be- 
ginning with  the  one  which  is  in  most  common  use. 

Oylinder  Electrical  Machine. — The  various  parts  of  this 
instrument  are  shown  in  Fig.  375.  A,  is  a  glass  cylinder 
which  is  made  to  revolve  by  the  turning  of  a  winch  con- 
nected by  a  crossed  belt  with  the  wheel  and  axle  attached  to 
the  two  axes  of  the  cylinder.  These  turn  in  the  supports 
seen  at  its  sides.  F,  is  the  negative  conductor  supported  by 
a  glass  pillar,  and  having  on  the  side,  nearest  to  the  cylinder, 
the  rubber  or  leather  cushion  which  presses  against  its  sides. 
The  cushion  has  attached  to  it  the  silk  flap  G,  which  extends 
nearly  over  the  upper  part  of  the  cylinder's  circumference. 
Below,  a  screw  passing  through  two  nuts,  is  so  placed  as  to 
increase  or  diminish  the  friction  of  the  rubber  upon  the  glass, 
by  making  the  distance  of  the  movable  pedestal  upon  which 
the  former  stands,  greater  or  less  from  the  main  support  of 
the  machine.  Upon  the  opposite  side  of  the  cylinder,  is  the 
27 


ki 


410 


THE  CYLINDER  ELECTRICAL  MACHINE. 


positive  or  prime  conductor  C,  being,  like  the  other  conductor, 
a  hollow  cylinder  of  brass  or  other  metal,  also  insulated  and 

Fig.  375. 


provided  with  balls  for  the  transference  of  the  influence,  but 
having  instead  of  a  rubber,  a  collector  E,  provided  with  sharp 
points  or  prongs  which  are  almost  in  contact  with  the  surface 
of  the  cylinder. 

The  machine  is  often  simplified  by  having  the  handle  at- 
tached directly  to  the  axis  of  the  cylinder,  and  by  dispensing 
with  the  screws  and  other  parts  of  the  arrangement  in  a  way 
to  be  hereafter  described.  As  arranged  in  the  figure,  it  is 
made  to  develop  electricity  by  turning  the  winch,  which 
causes  the  smaller  wheel  and  the  attached  cylinder  to  revolve 
with  accelerated  rapidity.  By  the  friction  of  the  glass  upon 
the  rubber — covered  with  a  metallic  amalgam — the  electricity 
naturally  present  in  the  latter  is  supposed  to  be  decomposed, 
its  positive  element  becoming  attached  to  the  glass  and  its 
negative  one  to  the  cushion.  The  former,  prevented  from 
escaping  by  the  non-conducting  silk,  is  carried  around  with  the 
glass,  and — after  a  series  of  alterations  by  induction,  of  the 
equilibrium  of  that  portion  of  the  fluid  naturally  present  in 
the  conductor — finally  by  passing  into  it  through  the  highly 
conducting  collector,  fills  it  with  positive  or  vitreous  electri- 


THE  CYLINDER  ELECTRICAL  MACHINE.  411 

city,  which  can  be  drawn  off  from  it  into  other  conducting 
bodies,  either  insensibly  or  in  sparks.  The  negative  conductor 
while  insulated,  becomes  in  the  same  way  negatively  electrified, 
and  is  capable  of  giving  sparks  to,  or  rather  receiving  them 
from,  other  bodies  oppositely  influenced:  but  while  uncon- 
nected with  the  earth,  it  gives  off  to  the  cylinder  but  a  small 
amount  of  its  positive  component,  and  it  soon  returns  to  its 
former  state  of  equilibrium,  from  its  negative  electricity  being 
neutralized  by  the  positive  kind  of  the  prime  conductor,  which 
passes  back  over  the  surface  of  the  cylinder,  and  which  also 
reaches  it  by  other  sources  of  imperfect  conduction. 

If  much  positive  excitement  is  desired,  the  conductor  to 
which  the  rubber  is  attached,  must  be  kept  in  connection  with 
the  earth,  or  a  conducting  surface  in  contact  with  it,  by  a 
metallic  chain  or  wire.  When,  on  the  contrary,  the  intention 
is  to  obtain  negative  electricity  from  its  proper  collector, 
the  prime  conductor  must  be  made  to  communicate  with  the 
earth  by  the  same  means. 

Not  a  little  care  is  necessary  in  the  construction  and  ar- 
rangement of  all  the  parts  of  the  electrical  machine.  The 
cylinder  should  be  strong  and  well  annealed,  particularly  at 
the  projections  which  are  to  be  received  into  the  caps  forming 
the  centres  of  motion.  Its  sides  should  be  as  straight  as  pos- 
sible, so  as  to  be  adapted  uniformly  to  the  rubber,  and  to 
allow  it  to  run  truly  upon  its  axis.  Moisture  should  be  care- 
fully expelled  from  its  interior,  by  a  long-continued  exposure 
to  a  current  of  dry  and  warm  air,  and  the  lateral  orifices 
should  be  hermetically  closed  by  cementation  to  the  caps 
which  form  the  axes.  Cylinders  of  the  proper  size  and  form 
are  sold  in  our  glass-works  and  shops,  but  when  one  cannot 
be  obtained,  a  properly  made  glass  jar  or  bottle,  may  be  so 
attached  to  a  wooden  or  metallic  axis — passing  through  its 
mouth  and  through  a  hole  in  its  concave  bottom — as  to  make 
a  very  good  substitute. 

The  cushion,  or  rubber,  consists  of  a  pad  made  of  buck- 
skin or  soft  leather,  stuffed  with  horse-hair  or  similar  material, 
and  mounted  upon  a  support  which  is  in  connection  with  the 
negative  conductor.  In  the  greater  number  of  cases,  there 
is  no  occasion  for  the  presence  of  this  latter  part  of  the  ma- 
chine. When  positive  electricity  alone  is  to  be  collected,  the 
rubber  may  be  with  propriety  attached  to  a  wooden  support, 
which  is  by  any  means  made  capable  of  being  drawn  towards, 


412  THE  CYLINDER  ELECTRICAL  MACHINE. 

or  separated  from,  the  cylinder.  The  flap  attached  to  the 
rubber  is  generally  made  of  unoiled  black  silk,  and  it  should 
reach  nearly  to  the  extremities  of  the  pointed  collector,  so 
that  its  full  effect  may  be  produced,  namely,  the  preventing 
of  the  transmission  of  electricity  into  the  air  before  it  reaches 
the  prime  conductor. 

The  exciting  power  of  the  rubber  is  much  increased  by 
spreading  upon  its  surface  an  amalgam^  mixed  with  unctuous 
matter,  to  make  it  adherent.  A  mixture  of  the  amalgam  of 
tin — scraped  from  the  back  of  a  mirror — with  a  little  lard, 
answers  the  purpose  very  well ;  but  the  best  kind,  and  that 
in  most  common  use,  is  made  by  adding  to  six  parts  of  mer- 
cury, previously  heated  in  a  crucible,  a  melted  alloy  of  two 
parts  of  zinc  and  one  part  of  tin,  and  by  rapidly  stirring  the 
mixture  until  it  is  cold,  when  it  can  be  readily  reduced  to 
powder.  Before  applying  it,  the  cushion  is  cleaned  and 
roughened  by  scraping,  and  is  greased  with  a  little  lard  or 
tallow.  Some  of  the  amalgam  is  then  intimately  mixed  in  a 
mortar  with  a  quantity  of  unctuous  matter  suflficient  to  make 
it  of  a  pasty  consistence,  and  enough  of  this  is  smeared  upon 
the  surface  of  the  rubber  to  give  it  a  metallic  appearance. 
The  cylinder  is  then  to  be  turned  rapidly  while  the  cushion  is 
forcibly  pressed  upon  it,  and  after  the  amalgamated  surface 
has  been  compressed  and  equalized  by  the  friction,  the  super- 
abundance of  grease  and  metal  is  wiped  off  from  the  surface 
of  the  cylinder  and  flap.  The  impregnation  of  the  latter 
with  a  small  portion  of  the  amalgam,  and  the  presence  upon 
the  surface  of  the  former,  of  minute  spots  of  it,  are  rather  ad- 
vantageous than  otherwise.  The  mode  in  which  the  amalgam 
assists  in  the  production  of  electricity  is  not  precisely  known, 
but  it  is  supposed  that  its  oxidation  by  friction  and  exposure 
to  air  has  something  to  do  with  it.  The  facts  that  amal- 
gams of  gold  and  other  difficultly  oxidable  metals  do  not  in- 
crease the  development  of  the  power,  and  that  an  atmosphere 
of  carbonic  acid  surrounding  the  machine  prevents  it  entirely, 
seem  to  favor  this  belief. 

The  conductors  of  the  two  kinds  of  electrical  influence  are 
generally  of  the  form  shown  in  the  figure,  and  usually  con- 
sist of  hollow  cylinders  of  brass  or  tinned  iron.  They  may 
be  turned  out  of  wood  and  covered  smoothly  with  tin  foil, 
which  answers  the  same  purpose,  as  it  has  been  found  that 
the  electricity,  even  when  in  a  state  of  great  tension,  is  con- 


THE  PLATE  ELECTRICAL  MACHINE.  419 

centrated  chiefly  in  the  surface.  Small  brass  knobs  or  balls 
are  attached  by  thick  wires  to  the  sides  and  tops  of  the  con- 
ductors, for  the  purpose  of  drawing  off  sparks  from  the  ma- 
chine. In  the  absence  of  these,  leaden  bullets  with  wires 
inserted,  may  very  well  be  used.  The  conductors  are  sup- 
ported upon  glass  pillars  or  tubes,  which  are  coated  with  a 
varnish  of  shell-lac.  These,  as  well  as  the  caps  of  the  cylin- 
der, are  firmly  inserted  into  their  connections  by  means  of 
the  cement  described  upon  page  276. 

The  Plate  Electrical  Machine. — The  power  of  this  de- 
scription of  machine  is  believed  to  be  much  greater  than  that 
of  the  kind  in  which  the  cylinder  is  used.  The  objection  to 
its  employment  has  been  the  diiOficulty  of  insulating  the  cush- 
ions, and  consequently  of  obtaining  negative  electricity.  It 
has,  therefore,  been  chiefly  employed  for  class  demonstrations. 
Dr.  Hare,  in  his  Qompendium^  describes  one  which  he  has 
successfully  used,  a  long  time,  for  the  purpose  of  producing 
both  kinds  of  influence.  The  machine  is  represented  in  Figs. 
376  and  377,  and  the  following  is  the  description : — 

"  The  plate  B  (thirty-five  inches  in  diameter)  is  supported, 
as  represented  in  the  figure,  upon  an  upright  iron  bar,  about 
an  inch  in  diameter,  covered  by  a  very  stout  glass  cylinder 
A,  four  inches  and  a  half  in  diameter,  and  sixteen  inches  in 
height,  open  only  at  the  base,  through  which  the  bar  is  intro- 
duced, so  as  to  form  its  axis.  The  summit  of  the  bar  is  fur- 
nished with  a  block  of  wood,  turned  to  fit  the  cavity,  formed 
at  the  apex  of  the  cylinder,  and  cemented  therein.  The  ex- 
ternal apex  of  the  cylinder  is  cemented  into  a  brass  cap, 
which  carries  the  plate.  The  glass  cylinder  is  liable  to  no 
strain.  It  is  only  pressed  where  it  is  interposed  between  the 
block  of  wood  within,  and  the  brass  cap  without.  The  remain- 
ing portion  of  the  cylinder  bears  only  its  own  weight,  while  it 
effectually  insulates  the  plate  from  the  iron  axis.  The  brass 
cap  is  surmounted  by  a  screw  and  flange,  by  means  of  which, 
a  corresponding  nut,  and  disks  of  mahogany,  the  plate  is  fast- 
ened. A  square  table  serves  as  a  basis  for  the  whole.  The 
iron  axis,  descending  through  the  top  of  the  table,  is  furnished 
with  a  wooden  wheel  of  about  twenty  inches  in  diameter  D, 
(Fig.  377,)  and  terminates  below  this  wheel  in  a  brass  step  S, 
supported  on  the  cross  of  wood,  which  ties  the  legs  of  the 
table  diagonally  together.  The  wheel  D,  is  grooved  and 
made  to  revolve  by  a  band,  which  proceeds  from  around  a 


414 


THE  PLATE  ELECTRICAL  MACHINE. 


vertical  wheel  W,  outside  of  the  table.     This  external  wheel 
has  two  handles,  by  means  either  of  one  or  both  of  which  it 

Fig.  376. 


may  be  turned.     It  is  supported  on  two  strips  of  wood  G  G, 
which,  by  appropriate  screws  (represented  at  S  S,  Fig.  377), 


Fig.  377. 


THE  PLATE  ELECTRICAL  MACHINE.  415 

may  be  protruded,  lengthwise,  from  cases,  which  confine  them 
from  moving  in  any  other  direction.  Consequently,  the  dis- 
tance between  the  wheels  may  be  varied  at  pleasure,  and  the 
tension  of  the  band  adjusted. 

"Nearly  the  same  mode  of  insulation  and  support,  which  is 
used  for  the  plate,  is  used  in  the  case  of  the  conductors. 
These  consist,  severally,  of  arched  tubes  of  brass,  of  about  an 
inch  and  a  quarter  in  diameter,  which  pass  over  the  plate 
from  one  side  of  it  to  the  other,  so  as  to  be  at  right  angles  to, 
and  at  a  due  distance  from,  each  other.  They  are  terminated 
by  brass  balls  and  caps,  which  last  are  cemented  on  glass 
cylinders  C  C  C  C,  of  the  same  dimensions,  nearly,  as  that 
which  supports  the  plate.  The  glass  cylinders  are  suspended 
upon  wooden  axes,  surmounted  by  plugs  of  cork,  turned  ac- 
curately to  fit  the  space  which  they  occupy.  The  cylinders 
are  surrounded  and  secured  below,  by  wooden  rings  screwed 
to  the  table.  In  this  way  the  conductors  are  efiectually  in- 
sulated, while  the  principal  strain  is  borne  by  the  wooden 
axes. 

"  Collectors  consist  of  hollow  hemispheres  of  sheet  brass, 
within  which  several  points  proceed  towards  the  plate  from 
their  centres  respectively,  where  they  are  attached  to  the 
knobs  K  K  K  K.  The  hemispheres  are  intended  to  diminish 
the  injurious  circulation  of  air. 

"  The  cushions  are  included  between  springs,  by  which  they 
are  made  to  press  with  an  elastic  force  upon  the  surfaces  of 
the  glass,  the  degree  of  the  pressure  being  regulated  by  a 
screw." 

Electrical  machines  of  whatever  kind,  act  to  the  greatest 
advantage  in  clear,  cold  and  dry  weather.  A  moist  and  warm 
condition  of  the  atmosphere  is  generally  unfavorable  to  their 
use,  but  various  circumstances, — of  which  unknown  meteoro- 
logical influences  are  probably  the  chief — oppose  the  electric 
excitement  even  in  an  apparently  propitious  state  of  the 
weather.  Care  should  be  taken  in  such  cases,  whatever  the 
condition  of  the  air,  that  the  communication  of  certain  parts 
of  the  apparatus  with  the  earth  be  as  perfect  as  possible. 
With  this  view,  when  either  kind  of  excitement  is  required, 
the  conductor  of  the  other  kind  may  be  connected  by  means 
of  a  chain  or  wire  with  the  water  or  gas  pipes  of  a  house,  or 
any  other  good  conducting  substances  which  penetrate  the 
moist  earth.     The  cylinder,  or  plate,  and  the  insulating  parts 


416  THE  LEYDEN  JAB. 

of  the  apparatus  should  be  free  from  moisture  or  dust,  which 
might  both  conduct  away  electricity,  and  to  ensure  perfect 
dryness  of  all  parts  of  the  machine,  it  should  be  placed  before 
a  fire  or  upon  a  stove  or  sand  bath,  and  be  thoroughly  rubbed 
and  dried  with  a  piece  of  warm  flannel,  taking  care  that  the 
amount  of  heat  applied  be  not  great  enough  to  melt  the  ce- 
ment, which  is  employed  to  connect  the  various  parts. 

It  is  an  indication  that  the  machine  works  properly,  if  after 
several  revolutions  of  the  cylinder  or  plate,  the  approach  of  a 
metallic  ball  or  of  the  knuckle  to  a  part  of  the  insulated  con- 
ductor, causes  a  vivid  spark  to  dart  with  a  crackling  noise 
from  the  latter  to  the  former.  The  size  of  the  spark  and 
loudness  of  the  report  are  of  course  dependent  in  a  measure 
upon  the  magnitude  and  power  of  the  machine. 

The  Leyden  Jar. — This  instrument,  shown  in  Fig.  378,  is 
the  one  employed  for  the  purpose  of  accumulat- 
Fig.  378.         ing  electricity  by  induction,  and  is  the  agent 
Q  chiefly  made  use  of  for  laboratory  purposes.  It 

T  usually  consists  of  a  wide-mouthed  jar  of  thin 

^HpN,  glass,  coated  with  tin  foil  both  upon  the  inner 

^u«»j  and  the  outer  side  of  the  bottom  and  the  lower 

jLja  two-thirds  of  the  circumference.  The  stopper 
JJSk  is  made  of  cork  or  dry  wood,  well  varnished 
IIB  and  cemented  tightly  in  its  place.    Through  its 

|||H|  centre,  a  wire  or  rod  passes,  which,  either  with 

lil^B__  ^^  without  a  chain  attached,  is  in  close  contact 
MMKtK^  below  with  the  inner  lining  of  the  jar,  and 
which  terminates  above  in  a  smooth  metallic 
ball.  That  part  of  the  glass  which  is  not  covered  with  tin 
foil  is  usually  painted  over  with  a  coating  of  shell-lac  or  com- 
mon spirit  varnish.  The  jar  made  use  of  in  the  laboratory, 
need  not  ordinarily  exceed  a  quart  in  capacity.  The  ball 
upon  the  top  of  the  rod  should  be  at  least  an  inch  in  dia- 
meter, and  the  latter  should  be  so  firmly  fixed  in  its  place  as 
not  to  be  dislodged  from  its  connection  with  the  stopper  or 
the  bottom  of  the  jar,  by  any  change  of  position. 

A  common  phial  containing  iron  filings — into  which  is 
plunged  a  wire  which  passes  through  the  cork,  and  is  inserted 
into  a  bullet  above — and  coated  outside  with  tin  foil  up  to  the 
level  of  the  metal  within,  makes  a  very  efficient  apparatus. 

The  Leyden  Phial  is  charged  by  placing  its  ball  in  contact 
with  that  conductor  of  the  machine  which  contains  the  kind 


THE  LEYDEN  JAR.  417 

of  electricity  which  it  is  intended  to  accumulate  in  its  inner 
coating,  while  the  outer  metallic  surface  is  in  connection  with 
the  earth.  This  is  most  conveniently  performed  by  grasping 
the  jar  in  the  hand,  and  presenting  the  knob  to  the  conductor 
during  the  continued  turning  of  the  winch. 

The  electricity  often  accumulates  in  the  inner  coating  until 
its  tension  becomes  so  great  that  the  equilibrium  of  both  coat- 
ings is  restored  by  a  discharge  taking  place  from  one  surface  to 
the  other  ;  that  amount  which  is  in  excess  leaping  over,  as  it 
were,  the  intervening  non-conducting  surface  of  glass.  When 
one  kind  of  electricity  is  collected  in  the  interior,  the  opposite 
sort  is  produced  in  the  exterior  coating,  or — in  accordance  with 
the  theory  which  admits  the  existence  of  only  one  kind — 
when  it  is  in  excess  in  the  inside,  it  is  deficient  in  the  same 
ratio  upon  the  outside.  The  tendency  is  then  always  to  re- 
store that  neutrality,  or  natural  order  of  things  in  which  the 
influence  is  not  made  evident  to  the  senses;  but  in  a  good 
Leyden  jar,  the  parts  should  be  so  arranged  as  to  permit  the 
collection  of  a  large  amount  of  electricity  before  a  sponta- 
neous discharge  takes  place.  If  the  jar,  before  becoming 
highly  charged,  permits  such  an  escape,  it  is  usually  an  evi- 
dence that  there  is  a  hole  or  crack  in  the  glass,  that  the  un- 
covered surface  has  become  a  partly  conducting  one  from  the 
presence  upon  it  of  moisture  or  dust,  or  finally  that  the  outer 
metallic  coating  extends  up  so  far  as  to  allow  of  the  easy 
passage  of  a  spark  to  it  from  the  rod  or  ball.  The  last  con- 
dition can  be  altered  by  lessening  the  height  of  the  outer 
covering  of  foil,  taking  care  to  reduce  that  which  is  within, 
also  to  the  same  level.  To  expel  moisture  and  dust,  the  vessel 
should  be  warmed  and  wiped,  as  before  directed  for  other  parts 
of  the  apparatus. 

The  retention  for  some  time,  of  the  charge,  by  the  Leyden 
jar  is  often  a  matter  of  great  importance  in  the  chemical 
applications  of  electricity.  A  jar,  of  the  capacity  above  men- 
tioned, when  dry,  warm,  and  fully  charged,  should  after  a 
lapse  of  ten  minutes,  give  a  spark  at  least  half  an  inch  in 
length,  to  the  ball  of  a  discharging  rod,  the  ball  being  one- 
third  of  an  inch  in  diameter. 

The  power  of  the  jar  is  dependent  on  the  amount  of  the 
coated  surface,  and  the  thinness  of  the  glass. 

The  Electrical  Battery. — This  is  an  arrangement  by  which 
the   metallic   surfaces  of  the   Leyden  jar   are   greatly  in- 


418 


THE  ELECTRICAL  BATTERY. 


creased  in  size,  and  by  which  the  intensity  of  the  shock  and 
discharge  is  multiplied  to  almost  any  extent  desired.  A 
number  of  Ley  den  jars  prepared  in  the  usual  manner,  are 
placed  in  a  box  which  is  lined  with  tin  foil  or  other  metallic 
coating.  The  vessels  are  placed  in  close  contact,  or  are  made 
to  connect  with  each  other  externally,  by  the  interposition  of 
metallic  or  coated  partitions,  and  the  inner  coatings  are  made 
to  communicate  by  means  of  metallic  rods  or  chains,  connected 
with  the  wires  going  from  their  interior.  The  whole  is  equi- 
valent to  a  single  large  jar,  and  may  be  charged  and  dis- 
charged with  equal  facility.     Fig.  379. 

Fig.  379. 


The  hook,  seen  in  the  front  of  the  box  which  contains 
the  series,  is  attached  to  the  metallic  outer  lining. 

When  the  battery  is  to  be  used,  it  should  be  ascertained 
that  all  the  outside  coatings  are  in  proper  connection  with 
each  other,  and  that  the  inner  surfaces  communicate  through 
their  appropriate  mountings  and  wires,  and  that  no  wires, 
threads,  water,  or  other  conducting  substances  extend  in  any 
way  from  the  inner  to  the  outer  parts  of  the  apparatus.  No 
filamentous  or  pointed  body,  or  projecting  piece  of  metal, 
should  be  allowed  to  remain  very  near  the  battery  while  it  is  in 
operation.  The  battery  is  charged  by  connecting  one  of  the 
wires  or  knobs  which  are  in  contact  with  the  inner  coating  of 
the  jars,  by  means  of  a  chain  or  wire,  with  the  prime  or  ne- 
gative conductor  of  the  electrical  machine  while  it  is  in  ope- 
ration. It  is  both  filled  and  discharged  in  the  same  way  as 
the  Leyden  jar,  and  all  its  operations  are  those  of  that  vessel 
upon  a  greater  scale. 

During  the  charging  of  a  battery,  a  difi'usion  of  electricity 


THE  DISCHARGER. 


419 


sometimes  takes  place  over  that  part  of  the  uncoated  glass, 
which  is  near  the  edge  of  the  foil.  This  is  not  entirely  re- 
moved upon  the  discharge  of  the  coated  part,  but  afterwards 
gradually  returns  to  the  coating  and  recharges  the  battery, 
often  to  a  considerable  extent.  Hence  if  after  the  discharge 
of  a  battery,  it  be  left  for  a  few  minutes  with  the  two  coatings 
unconnected,  it  will,  upon  the  application  of  the  discharger, 
give  a  considerable  spark.  This,  which  is  the  residual  charge, 
is  discharged  in  the  same  way,  when  the  Leyden  jar  is  used. 

The  Discharger. — A  discharge  between  the  oppositely  elec- 
trified surfaces  of  the  jar  may  be  effected  by  bringing  one 
hand  in  contact  with  the  external  coating,  and  touching  the 
knob  with  a  knuckle  of  the  other.  In  this  case  the  person 
receives  a  shock  in  his  arms,  and  if  the  surfaces  are  large  or 
well  filled  with  electricity,  he  experiences  a  painful  passage 
of  this  shock  through  the  shoulders  and  chest.  A  battery 
ordinarily  charged,  should  never  be  discharged  in  this  way,  as 
serious  and  even  fatal  results  might  follow. 

The  instrument,  shown  in  the  figure,  is  called  a  discharger 
and  is  used  to  complete  the  circuit  between  the  opposite  coat- 
Fig.  380. 


ings  of  both  the  jar  and  the  battery.     The  rods  R,  R,  are  so 
united  with  a  hinge  that  the  balls  may  be  made  to  come  in 


420  THE  ELECTROPHORUS. 

contact  with  the  surfaces,  or  to  be  removed  from  them  by 
means  of  the  insulating  glass  handles,  which  are  attached  to 
the  legs.  This  arrangement  gives  the  power  of  discharging  a 
jar  of  almost  any  size,  by  removing  or  approximating  the 
handles.  A  very  effectual  and  cheap  discharger  is  made  of  a 
piece  of  thick  wire,  about  twelve  inches  long,  curved  and  ter- 
minated by  a  bullet  at  each  end. 


OTHER  MEANS  OF  PRODUCING  ELECTRICITY. 

The  Ulectrophorus. — This  important  instrument,  Figure 
381,  may  in  many  cases  be  made  to  take  the  place  of  the 

common    electrical    machine.      A 

Fig-  381.  mixture  of  equal  parts  of  common 

r\  resin,  shellac  and  Venice  turpen- 

jl  tine,  is  melted  and  kept  in  a  state 

,  §  of  fusion  at  a  temperature  between 

^^j^^M^^^^^      230°  and  240°  of  Fahrenheit,  until 

|r^      ^t^^^^^^^    nearly  all  evolution  of  vapor  has 

^^^^^^^^^^^^^p    ceased  and  the  fluid  is  quiet.     It 

^ mmmni^^'^     jg  allowed  to  cool  to  the  point  of 

thickening,  and  is  then  poured  care- 
fully, so  as  to  avoid  the  formation  of  air  bubbles,  into  a  circular 
metallic  tray  or  dish,  of  about  nine  or  twelve  inches  in  diameter, 
and  half  an  inch  in  depth.  The  resinous  surface  should  be  as 
even  and  smooth  as  possible.  A  wooden  box,  or  a  receptacle 
made  by  placing  upon  a  smooth  board  a  wooden  hoop,  are 
less  costly  and  do  not  expose  the  resin  to  the  risk  of  cracking 
from  the  sudden  contraction  of  the  metal,  which  is  apt  to 
occur  after  its  expansion  by  heat.  Upon  the  smooth  surface 
formed  by  the  cooled  mixture,  is  placed  a  metallic  disk,  or  one 
of  wood  smoothly  covered  with  tin  foil,  either  of  which  is 
provided  with  an  insulating  handle  of  glass  or  sealing  wax, 
which  is  inserted  in  its  centre,  above.  This  disk  should  be 
somewhat  less  in  diameter  than  the  surface  of  resin.  The  top 
has  usually  attached  near  its  edge,  a  wire  terminating  in  a 
metallic  ball,  from  which  the  spark  is  taken. 

When  this  electrophorus  is  used,  the  cover  is  removed,  and 
the  surface  of  the  resin  having  been  dried  and  slightly 
warmed,  is  rubbed  or  whipped  briskly  with  a  piece  of  dry 
flannel,  a  silk  handkerchief,  or  the  fur  of  a  cat  or  hare's  foot. 


Henley's  quadrant  electrometer.  421 

After  excitation  by  this  means,  the  cover  is  lifted  by  its 
handle — also  dry — and  is  replaced  upon  the  surface  of  the 
resin.  A  spark  will  now  pass  from  the  knob  of  the  cover  to 
the  knuckle,  or  a  metallic  body  held  near  it.  Upon  raising 
the  cover  again,  another  spark  of  greater  intensity  than  the 
first  will  be  received.  A  spark  like  the  first,  will  be  given  by 
the  knob  after  the  replacing  of  the  cover,  and  again  upon  its 
withdrawal,  one  similar  in  character  to  the  second  will  be 
given  ofi",  and  in  this  way  the  experiment  may  be  repeated 
almost  indefinitely  if  the  weather  is  favorable. 

The  action  of  the  machine  is  explained  in  this  manner. 
The  negatively  excited  cake  of  resin  acts  inductively  upon 
the  electricity  inherent  in  the  cover,  attracting  and  combining 
with  its  positive  element,  and  repelling  its  negative  one,  which 
accumulates  in  the  upper  part  of  the  cover.  When  the  top 
of  the  cover  is  touched,  the  negative  electricity  escapes,  and 
the  positive  remains  in  combination  with  the  negative  kind  of 
the  resin,  as  long  as  the  latter  is  covered  by  the  metallic 
plate.  But  upon  lifting  this  by  the  insulating  handle,  the 
positive  excitement  is  in  its  turn  set  free,  and  given  oiF  in 
sparks  from  the  knob.  A  similar  succession  of  actions  goes 
on  for  some  time,  and  the  instrument  has  been  known  to  give 
sparks  for  weeks  without  being  freshly  excited. 

To  obtain  strong  positive  sparks,  it  is  necessary  to  touch 
the  cover  when  on  the  resin,  with  a  finger  or  other  conducting 
body,  and  to  remove  it  before  raising  the  cover.  To  obtain 
the  strongest  negative  sparks,  the  cover  when  raised,  should 
be  discharged  of  all  its  electricity  against  the  hand  or  other 
body  before  it  is  again  placed  upon  the  surface  of  the  resin. 


INSTRUMENTS  FOR  DETECTING  AND  MEASURING  ELECTRICITY. 

Henley's  Quadrant  Electrometer. — This  instrument,  chiefly 
used  to  determine  the  amount  of  electricity  present  in  the 
conductor  and  in  the  Leyden  jar,  consists  of  a  semicircle  of 
ivory  or  of  wood  covered  with  white  paper,  which  is  graduated 
into  180  degrees,  and  fixed  at  its  base  to  a  wooden  column. 
In  the  centre  of  the  semicircle  there  is  a  pin  upon  the  column, 
from  which  a  movable  radius  terminated  by  a  pith  ball  is  sus- 
pended. The  column  may  be  fixed  in  a  hole  in  the  conductor. 
Upon  working  the  machine,  the  column  and  the  ball  being 


422 


BENNET  S  ELECTROMETER. 


alike  affected,  the  latter  with  its  radius  is  repelled  from  the 
former,  and  by  the  amount  of  the  divergence  the  force  is 
exhibited  in  degrees.  By  means  of  this  instrument,  we  are 
enabled  to  ascertain  when  a  jar,  or  battery  in  contact  with 
the  conductor,  is  sufficiently  electrified.  During  the  accumu- 
lation in  the  inner  coating,  the  electricity  is  retained  forcibly 
by  the  attraction  of  the  contiguous  and  oppositely  electrified 
surface,  and  will  not  be  given  off  to  an  insulated  body,  or  one 
which  is  not  in  connection  with  the  outer  coating.  But  in 
proportion  as  it  ceases  to  be  retained  by  this  inductive  action^ 
and  accumulates  in  the  conductor,  it  raises  the  index  of  the 
electrometer,  often  to  a  considerable  height.  When  a  battery 
has  received  its  greatest  amount  of  charge,  the  ball  seldom 
rises  above  40°  or  50°,  as  the  tension  of  the  electricity  never 
equals  that  of  a  single  jar,  probably  on  account  of  the  larger 
surface  exposed  to  induction. 

Haiiy's  Electroscope  has  already  been  described  under  the 
head  of  the  Blowpipe  at  page  383. 

Bennetts  Electrometer, — This  instrument,  more  properly 
called  an  electroscope,  as  it  detects,  rather  than  measures 
electricity,  is  exceedingly  delicate  in  its  indications.  It  con- 
sists in  part  of  a  glass  cylinder,  which  may  be  similar  in  form 
to  the  one  shown  in  the  drawing.     A  circular  brass  cap  C, 

covers  tightly  the  vessel,  and  to  its 
centre  is  attached  a  metallic  rod, 
enclosed  in  a  glass  tube  which  is 
well  varnished  with  shell-lac,  and 
having  attached  to  its  ends  two 
slender  strips  of  gold  leaf,  hanging 
parallel  to  each  other.  Two  strips 
of  tin  foil  T  T,  are  pasted  upon  the 
inside  of  the  glass,  with  their  upper 
ends  a  little  above  the  level  of  the 
depending  extremities  of  gold  leaf, 
and  their  lower  ends  connected  with 
the  metallic  bottom  of  the  glass 
cylinder.  When  an  electrified  body 
is  made  to  approach  the  cap  of  the 
electrometer,  the  gold  leaves  will 
diverge,  and  if  the  excitement  be 
sufficiently  powerful,  will  touch  the  tin  foil  and  then  return  to 
their  former  state  of  rest. 


Fig.  382. 


bennet's  electeometer.  423 

The  delicacy  of  Bennet's  electrometer  is  much  increased  by 
the  addition  of  two  metallic  disks,  one  having  its  centre  sol- 
dered to  the  side  of  the  cap  of  the  instrument,  being  in  a 
perpendicular  position,  and  the  other  being  attached  to  a  rod 
which  is  connected  with  the  metallic  foot  of  the  instrument 
by  a  hinge,  so  that  it  may  be  placed  parallel  to  the  other 
disk,  and  so  near  as  almost  to  touch  it  without  actually  doing 
so.  The  presence  of  electricity  in  the  metallic  cap,  and  its 
disk,  induces  the  opposite  kind  in  the  contiguous  metal,  which 
is  then  to  be  removed  a  few  inches  from  its  former  position. 
As  this  disk  is  connected  with  the  base  of  the  instrument, 
and  of  course  with  the  tin  foil  upon  the  inside  of  the  glass, 
that  becomes  also  oppositely  electrified  from  the  cap,  the  con- 
nected gold  leaves  of  which  diverge  to  a  much  greater  degree 
than  in  the  simple  instrument.  This  is  called  the  condensing 
electrometer. 

Bennet's  electrometer  is  the  one  in  most  common  use,  and 
many  circumstances  of  interest  in  reference  to  its  employment 
are  worthy  of  note,  particularly  those  connected  with  the 
means  of  ascertaining  the  kind  of  electricity  which  causes  its 
gold  leaves  to  diverge. 

If  an  insulated  conducting  body  containing  electricity,  such 
as  the  prime  conductor  of  the  electrical  machine,  is  made  to 
approach  or  to  touch  the  cap  of  the  electrometer,  the  leaves 
diverge  to  a  greater  or  less  degree,  in  proportion  to  the  ten- 
sion of  the  electricity  in  the  body,  and  remain  separated, 
gradually  returning  to  their  former  position  as  the  influence 
passes  off.  In  examining  the  condition  of  a  body  supposed 
to  be  highly  electrified,  care  must  be  taken  not  to  make  it 
approach  the  cap  too  rapidly,  as  the  result  of  a  sudden  and 
powerful  communication  of  the  agent  is  very  often  the  im- 
mediate separation  and  tearing  of  the  gold  leaves.  When  a 
non-conducting  body,  electrically  excited, — a  piece  of  sealing 
wax,  for  instance, — is  brought  near  to,  or  in  contact  with  the 
top  of  the  instrument,  the  same  divergence  takes  place ;  but 
it  is  temporary,  as  upon  the  withdrawal  of  the  body  the 
leaves  come  together  again.  To  make  their  separation  as  last- 
ing as  in  the  former  case,  it  is  necessary  either  to  allow  the 
body  to  remain  for  a  time  upon  the  cap,  or  to  rub  it  over  its  sur- 
face, so  that  it  may  communicate  its  electricity  from  a  number 
of  points.  So  far,  the  electricity  of  either  kind,  imparted  to 
the  cap,  has  been  that  of  conduction.     But  if  the  electrified 


424  INDICATIONS  OF  THE  KIND  OF  ELECTRICITY. 

body  be  held  so  near  to  the  cap,  as  just  to  cause  the  diverg- 
ence of  the  leaves,  that  divergence  will  diminish  gradually 
until  the  leaves  finally  collapse.  If  now  the  body  be  removed 
to  such  a  distance  that  it  can  scarcely  afiiect  the  leaves,  they, 
after  coming  together,  will  often  gradually  diverge  as  before. 
This  second  separation  is  caused  by  induction,  and  when  it 
occurs,  the  opposite  kind  of  electricity  to  that  existing  in  the 
body  will  be  found  to  be  present  in  the  cap  and  leaves.  The 
same  effect  is  produced  by  touching  the  cap  with  the  hand, 
while  the  leaves  are  diverging  from  the  electricity  of  the 
excited  body,  by  removing  the  hand  after  the  collapse  occa- 
sioned by  its  first  contact,  and  by  then  withdrawing  the  elec- 
trified body,  as  before,  to  a  greater  distance  from  the  cap. 

It  is  well  known  that  a  piece  of  sealing  wax,  rubbed  with 
warm  flannel,  becomes  negatively  electrified  and  that  a  glass 
tube  rubbed  with  a  silk  handkerchief,  becomes  positively  af- 
fected. These  facts  present  us  with  the  means  of  determining 
the  kind  of  electricity  which  is  transferred  to  the  cap  and  leaves 
of  Bonnet's  electroscope.  If — after  the  leaves  have  been  made 
to  diverge  by  the  approximation  to  the  cap  of  an  excited 
body — the  presence  upon  the  top,  of  a  piece  of  rubbed  sealing 
wax  makes  the  divergence  greater,  the  electricity  in  the  body 
is  negative.  If  however,  the  leaves  approach  each  other 
slowly,  or  collapse  at  once,  the  electricity  is  more  or  less  posi- 
tive. In  the  same  way,  a  warm  tube  of  glass,  rubbed  with  a 
silk  handkerchief,  will  increase  the  separation  of  the  positively 
electrified  leaves,  and  diminish  or  annul  it  when  they  are  ne- 
gatively excited. 

Coulomb's  Electrometer. — All  the  instruments,  above  de- 
scribed, indicate  the  presence  of  electricity,  but  give  little  idea 
of  its  quantity.  Coulomb's  torsion  balance  gives  us  an  ap- 
proximation at  least  to  a  means  of  accurately  measuring  it,  or 
rather  of  comparing  the  amount  of  it  found  in  one  body  with 
that  existing  in  others,  or  in  the  same  body,  at  different 
times.  This  instrument,  as  represented  in  Fig.  383,  from 
Golding  Bird's  Natural  Philosophy,  consists  of  a  slender 
beam,  or  thread  of  shell-lac  B,  having  a  gilt  pith-ball  attached 
to  one  end,  and  a  little  vane  of  paper  to  the  other,  and  sus- 
pended at  its  centre  by  a  fine  metallic  wire,  or  what  is  better, 
a  delicate  filament  of  spun  glass.  This  ascends  in  a  cylin- 
drical or  square  frame  of  glass,  and  its  upper  end  terminates 


coulomb's  electrometer. 


425 


Fig.  383. 


Si^:^^^ 


in  a  key  D,  furnished  with  an  index,  the  whole  being  capable 
of  moving  easily  in  the  centre  of  the  circle 
G^  which  is  graduated  into  360°.  A  rod  of 
shell-lac  -F,  is  inserted  in  the  hole  E,  and 
is  prevented  from  falling  down  into  the 
glass  cylinder  which  surrounds  the  whole 
arrangement,  by  a  stop  at  E.  This  rod 
terminates  in  a  gilded  ball,  which  is  called 
the  carrier  ball,  as  it  is  used  to  convey  to 
the  electrometer  proper,  the  electricity  of 
the  excited  body.  When  this  instrument 
is  to  be  used,  the  rod  F  is  brought  into 
contact  with  the  excited  body ;  its  ball  ac- 
quires some  of  the  electricity,  and  upon 
being  placed  in  the  cage,  it  gives  a  part 
of  it  to  the  ball  of  the  lac  beam.  This 
having  now  the  same  kind  of  electricity,  is 
repelled  from  the  ball  of  the  rod  and  de- 
scribes a  certain  angle  to  its  former  posi- 
tion, which  it  retains  until  it  loses  its  electricity.  To  mea- 
sure the  amount  of  fluid  thus  acquired,  the  key  D,  to  which 
the  glass  thread  is  fastened,  must  be  turned  around,  until  by 
the  torsion  or  twisting  of  the  latter,  the  ball  of  B  is  made  to 
come  in  contact  with  that  of  F.  The  number  of  degrees  de- 
scribed by  the  index,  which  is  attached  to  the  revolving  key 
D,  gives  an  approximation  to  the  proportion  of  electricity 
derived  from  the  contact  of  the  ball  of  F  with  the  electrified 
body. 

A  more  simple  form  of  this  electronometer,  and  the  one 
ordinarily  described,  consists  of  a  lac  needle  with  a  gilt  ball 
at  each  end,  suspended  by  means  of  a  fine  untwisted  thread 
of  raw  silk,  which  is  fixed  at  top  to  a  micrometer,  by  means 
of  which  it  can  be  turned  around  any  number  of  degrees  re- 
quired. The  whole  is  encased  in  a  glass  vase  or  cylinder, 
with  a  tightly  fitting  top  of  glass,  through  a  hole  in  the  centre 
of  which  the  silk  passes,  the  micrometer  being  above.  Upon 
the  level  of  the  suspended  needle,  a  hole,  drilled  through  the 
sides  of  the  glass,  encloses  a  wire  having  a  metallic  ball  at 
either  end,  the  inner  one  being  nearly  in  contact  with  one  of 
the  pith  balls.  The  excited  body  is  made  to  approach  the 
outer  ball,  and  as  in  the  instrument  before  described,  the 
movable  knob  separates  from  the  other,  and  the  quantity 
28 


426  EUDIOMETRY. 

of  electricity  is  proportional  to  tlie  distance  to  which  it  is 
driven  off. 


APPLICATIONS  OF  ELECTRICITY. 

Eudiometry. — Electricity  proper  is  more  often  applied  in 
the  laboratory  of  the  chemist  to  the  analysis  of  gaseous  mix- 
tures, by  taking  advantage  of  its  power  of  exploding  certain  of 
these,  than  to  any  other  purposes.  It  is  employed  in  connec- 
tion with  the  eudiometer,  an  instrument  which  is  used  chiefly, 
as  its  name  indicates,  to  ascertain  the  purity  of  the  atmo- 
sphere, but  in  which  the  analysis  of  gases  containing  carbon 
and  hydrogen  is  also  occasionally  effected.  In  it,  these  latter 
are  made  to  unite  explosively  with  oxygen,  while  in  the  exami- 
nation of  the  atmosphere,  the  explosion  of  hydrogen  with  its 
constituent  oxygen,  and  the  consequent  production  of  water 
and  diminution  of  volume,  enable  the  chemist  to  determine 
the  proportion  of  its  ingredients.  It  would  be  foreign  to  our 
purpose  to  give  a  full  description  of  all  the  applications  of  eu- 
diometry, but  a  short  account  of  the  means  most  commonly 
employed,  particularly  in  reference  to  the  proper  mode  of  ap- 
plying the  electric  spark,  will  scarcely  be  at  variance  with  the 
practical  nature  of  this  work. 

The  Common  Eudiometer  is  a  short  tube  of  thick  glass, 
having  one  end  closed.  This  tube  is  graduated,  and  near  its 
closed  extremity,  two  stout  wires  of  platinum  or  other  metal, 
intended  for  the  transmission  of  the  spark,  are  inserted  in  the 
opposite  sides,  their  ends  inside  of  the  tube  being  a  short  dis- 
tance apart.  The  other  end  of  the  tube  serves  for  the  intro- 
duction and  escape  of  the  gas,  and  it  remains  constantly 
immersed  in  the  liquid  over  which  the  experiment  is  made, 
the  tube  being  supported  in  a  perpendicular  position.  The 
gas  to  be  subjected  to  the  spark,  is  generally  such  a  mixture 
as  will  inflame  explosively  at  once,  though  sometimes  a  gra- 
dual combination  of  some  of  its  elements  is  effected  by  means 
of  a  long-continued  succession  of  sparks.  The  tube,  being 
filled  with  water  or  mercury,  may  be  placed  over  the  trough; 
or  for  the  purpose  of  more  accurately  determining  the  level 
of  the  gas  in  the  way  about  to  be  described,  it  should  be  sup- 
ported over  a  glass  vessel  containing  the  proper  liquid.  The 
gases  are  then  successively  introduced  into  it,  in  the  proper 


THE  COMMON  EUDIOMETER. 


427 


proportions,  after  the  manner  described  upon  pages  134, 135. 
To  determine  their  volumes  with  the  utmost  degree  of  accu- 
racy, it  is  necessary  to  support  the  tube  by  a  forceps  or  a 
cork-lined  clamp,  as  represented  in  the  figure,  and  not  be- 

Fig.  384. 


tween  the  fingers,  so  that  their  temperature  and  volume  shall 
not  be  increased  by  the  heat  of  the  hand.  To  ensure  that  the 
gas  be  submitted  to  no  more  pressure  than  that  of  the  atmo- 
sphere, the  eudiometer  should  be  raised  in  such  a  manner 
that  the  interior  level  of  the  liquid  contained  in  it,  shall  be 
exactly  at  the  same  height  as  that  of  the  liquid  in  the  vessel 
outside.  In  order  to  secure  this,  it  is  necessary  that  the  eye 
of  the  observer  be  in  the  same  plane  as  the  two  levels  of  the 
liquid,  and  that  the  line  of  the  liquids  in  direct  contact  with 
the  glass  inside  and  outside  of  the  tube,  be  not  taken  as  the 
proper  standard.  It  must  be  recollected  that — as  the  edge 
of  a  surface  of  water,  in  contact  with  the  glass,  is  elevated 
above  its  true  level  by  capillarity,  and  that  of  mercury  in  the 
same  circumstances  is  depressed — the  lower  line  in  the  former 
case,  and  the  upper  one  in  the  latter,  will  give  the  true  position 
of  the  main  surfaces.  The  exterior  of  the  tube  is  now  wiped 
clean,  so  that  no  mercury  or  water  in  contact  with  the  wires, 
can  conduct  ofi*  the  electricity.  The  tube,  kept  upright,  should 
then  be  clasped  firmly  in  the  hand  by  its  middle,  and  its  lower 
end,  still  under  water,  should  be  closed  with  slight  force  by 


428  THE  EUDIOMETER. 

the  thumb  or  a  finger  of  the  unoccupied  hand.  This  permits 
the  descent  of  the  fluid,  which  is  driven  out  by  the  force  of 
the  explosion,  while  it  does  not  allow  its  too  sudden  return 
upon  the  subsequent  contraction  of  the  gaseous  contents  of 
the  tube,  or  the  escape  of  any  of  the  latter. 

In  using  the  eudiometer,  we  must  take  into  account  the 
relative  degree  of  explosibility  of  different  mixtures.  Thus  a 
mixture  of  oxygen  and  carbonic  oxide  expands  when  inflamed, 
much  less  than  one  of  oxygen  and  hydrogen  or  olefiant 
gas.  A  large  quantity  of  any  mixture  will  of  course  increase 
in  bulk  much  more  than  a  small  one.  The  whole  quantity  of 
gas  contained  at  first  in  the  tube,  should  be  at  least  so  small, 
that  after  expansion  it  shall  not  occupy  quite  the  whole  of  the 
eudiometer.  No  more  gas  should  be  introduced  for  detona-' 
tion  than  will  occupy  a  sixth  of  its  capacity  at  common  tem- 
peratures, and  generally  it  will  be  advisable  to  employ  much 
less. 

The  spark  which  is  intended  to  effect  the  detonation  or 
slow  union  of  the  gases  contained  in  the  tube,  may  be  derived 
from  the  electrophorus,  the  prime  conductor  of  the  electrical 
machine,  or  the  Leyden  jar,  the  power  of  the  last  two  being 
of  course  greater,  in  the  order  in  which  we  have  spoken  of 
them,  than  that  of  the  first.  When  the  electrophorus  is  em- 
ployed, one  of  the  wires  upon  the  side  of  the  eudiometer  is 
placed  in  connection  with  a  finger  of  an  assistant,  or  with  a 
metallic  chain,  the  other  end  of  which  hangs  in  the  trough  or 
vessel  over  which  the  tube  is  supported.  The  ball  of  an  ex- 
cited electrophorus  is  then  brought  near  to  the  other  wire,  and 
the  spark  obtained  from  it,  passing  from  wire  to  wire  through 
the  interior  of  the  tube,  inflames  the  mixture,  if  it  be  of  suffi- 
cient intensity,  and  if  all  the  other  circumstances  are  favora- 
ble. The  ball  upon  the  conductor  of  the  electrical  machine  may 
in  the  same  way  be  made  to  approach  one  of  the  wires,  with 
usually  a  more  powerful  effect.  The  employment  of  the  elec- 
trical machine  is  particularly  advantageous  when  it  is  desired 
to  pass  a  succession  of  sparks  for  a  considerable  time  through 
the  mixture,  for  the  purpose  of  effecting  a  gradual  combustion 
or  combination  of  the  gases  contained  in  the  tube.  The  use  of 
the  Leyden  jar  is  equally  convenient  for  a  single  contact  and 
much  more  apt  to  be  attended  with  success  on  account  of  the 
greater  size  and  force  of  the  spark.  One  of  the  wires  may  be 
connected  with  the  external  coating  of  the  jar,  by  means  of  a 


ure's  eudiometer.  429 

chain  or  hooked  wire,  and  a  discharger  or  other  conductor, 
applied  at  one  end  to  the  ball  of  the  phial,  may  be  brought 
near  the  other  wire.  When  other  means  of  connection  are 
not  at  hand,  the  operator,  at  the  risk  of  receiving  an  unpleasant 
shock,  may  grasp  the  jar  in  his  hand  and  apply  its  ball  to  one 
wire  of  the  eudiometer,  while  he  touches  a  finger  of  the  other 
hand  to  the  opposite  wire.  To  ensure  the  explosion  of  the 
mixture,  a  spark  of  the  largest  size  that  can  be  obtained  from 
the  electrical  instrument,  should  be  passed  through  it.  Very 
often,  although  a  sufficient  amount  of  electricity  is  given  off 
from  the  conductor  of  the  electrophorus  or  electrical  machine, 
its  effect  is  lessened  by  its  communication  from  wire  to  wire, 
as  an  electrical  brush,  or  in  a  succession  of  small  sparks.  To 
remedy  this  evil,  a  ball,  half  an  inch  or  more  in  diameter, 
should  be  placed  upon  the  outer  extremity  of  that  wire  which 
is  to  receive  the  spark,  and  the  latter  should  always  be  given 
off  from  the  surface  of  a  ball  of  considerable  size. 

The  wires  of  the  eudiometer  must  be  firmly  fitted  in  their 
places,  and  the  openings  in  the  glass  through  which  they 
enter  should  be  hermetically  closed  around  them.  Before 
filling  the  tube  with  gas,  it  must  also  be  ascertained  that  they 
are  perfectly  insulated.  When  the  detonation  is  effected  over 
water,  a  film  of  it  is  apt  to  adhere  to  the  glass  and  wires,  both 
internally  and  externally,  which  by  its  conducting  power, 
sometimes  diminishes  the  force  of  the  spark,  or  intercepts  it 
entirely.  To  prevent  this,  the  outside  of  the  tube  and  wires 
must  be  wiped  as  dry  as  possible  before  applying  the  conduc- 
tor. The  top  of  the  tube  should  be  gently  tapped  so  as  to 
shake  off  any  particles  of  moisture  adhering  to  it  within.  The 
perfect  transmission  of  a  large  spark  is  only  secured  by  the 
presence  of  the  balls  upon  the  ends  of  the  wire  and  discharger 
as  before  described. 

Ures  Eudiometer. — Analysis  of  gases  by  explosion  is  much 
more  conveniently  performed  by  means  of  Dr.  Ure's  syphon 
eudiometer,  shown  in  Fig.  385.  It  differs  from  the  other 
eudiometer  in  being  curved  like  the  letter  U,  but  like  it,  it 
has  the  part  intended  to  contain  the  gaseous  mixture,  gra- 
duated and  pierced  by  two  platinum  wires.  It  is  usually  about 
twenty  inches  in  length,  and  the  third  of  an  inch  in  internal 
diameter.  This  instrument,  like  the  other,  may  be  used  for 
the  analysis  of  various  gases  over  either  water  or  mercury, 


430 


UEE  S  EUDIOMETER. 


Fig.  385. 


but  as  it  is  applied  chiefly  to  that  of  atmospheric  air  over  the 
latter  liquid,  we  will  confine  ourselves  to  a 
short  account  of  this  employment  of  it. 
When  about  to  be  used  for  an  examination 
of  the  atmosphere,  it  is  filled  with  mercury, 
and  the  required  amount  of  air  is  intro- 
duced into  the  open  end,  which  is  inverted 
over  the  trough,  as  in  the  case  of  the  use 
of  the  other  form  of  tube.  This  end  is 
then  tightly  closed  with  the  finger,  and 
the  tube  is  turned  slowly  so  as  to  admit 
the  air  into  the  graduated  extremity.  The 
instrument  is  then  held  upright,  and  the 
amount  of  air  introduced  is  read  off  by 
looking  at  the  scale,  after  subjecting  it  to 
atmospheric  pressure  by  displacing,  with  a 
stick  thrust  in,  that  portion  of  mercury 
which  is  above  the  level  of  that  in  the  graduated  limb.  This 
having  been  accurately  done,  the  open  part  is  again  filled  with 
mercury,  closed  with  the  finger,  inverted  into  the  liquid,  and  an 
amount  of  pure  hydrogen  is  introduced  equal  as  nearly  as  can 
be  guessed  to  half  the  volume  of  the  air.  The  quantity  of  hy- 
drogen added  is  then  accurately  estimated  by  returning  the 
eudiometer  to  the  erect  position,  equalizing  the  surface  of  the 
mercury  as  before,  and  reading  oft'  its  level.  The  instrument 
is  then  held  in  the  way  represented  in  the  figure,  the  thumb 
firmly  closing  its  aperture,  and  the  knuckle  of  the  fore-finger 
touching  the  nearer  platinum  wire.  The  explosion  is  pro- 
duced by  the  aid  of  the  electrophorus,  prime  conductor,  or 
charged  jar,  as  before  described,  the  violence  of  the  expansion 
being  moderated  by  the  spring-like  action  of  the  air  contained 
in  the  open  limb.  The  level  of  the  mercury  is  again  equal- 
ized by  pouring  into  the  open  side  enough  of  it  to  produce 
that  result,  and  the  volume  of  the  gaseous  mixture  is  then 
finally  read  off. 

The  loss  in  volume  of  the  mixture,  which  is  produced  by  the 
explosion,  gives  by  a  very  simple  process,  the  amount  of  oxy- 
gen originally  contained  in  the  air.  As  hydrogen  unites  with 
oxygen  to  form  water  in  the  proportion  by  measure  of  two  to 
one,  one-third  of  the  diminution  must  be  due  to  the  oxygen  of 
the  air  introduced.  Thus,  if  100  measures  of  air  and  50  of 
hydrogen  have  been  introduced,  and  if  the  mixture  contain 


GALVANISM.  431 

only  87  measures  after  explosion,  the  diminution  has  been  that 
of  63  measures.  One-third  of  this  loss  is  equal  to  21  mea- 
sures, which  represents  the  amount  of  oxygen  in  the  100 
measures  of  the  air  first  introduced. 

The  precautions  spoken  of  in  reference  to  the  common  eu- 
diometer may  with  equal  propriety  be  applied  to  this. 


GALVANISM. 

AH  the  forms  of  apparatus  which  are  employed  for  the 
purpose  of  producing  a  continuous  electrical  current,  are  called 
galvanic  circuits,  and  those  in  common  use  consist  of  two 
metals,  one  more  oxidable  than  the  other,  and  of  a  liquid  which 
by  its  action  upon  the  readily  oxidized  or  active  metal,  causes 
the  development  of  the  influence.  The  old  voltaic  pile  and 
the  crown  of  cups  are  the  most  simple  examples  of  galvanic 
apparatus.  The  former  consists  of  a  series  of  disks  of  zinc, 
and  copper,  platinum  or  silver,  arranged  in  a  column,  each 
piece  of  different  metal  having  placed  between  it  and  its 
neighbor,  a  disk  of  cloth  or  paper  steeped  in  some  liquid, 
which  acts  chemically  upon  the  zinc.  The  crown  of  cups  is 
differently  arranged,  but  upon  the  same  principle.  A  number 
of  cups  are  placed  in  a  row  or  circle,  each  one  containing  an 
exciting  liquid,  such  as  dilute  sulphuric  acid,  and  a  plate  of 
zinc,  and  one  of  the  inactive  metal.  The  zinc  of  one  cup  is 
connected  by  a  wire  with  the  copper  or  other  metal  of  the 
next  cup,  and  the  zinc  of  that  is  also  connected  with  the  cop- 
per of  the  one  beyond  it.  The  two  external  plates  of  both 
kinds  of  series  have  wires  soldered  to  them,  which  are  called 
the  poles.  In  this  way  a  communication  exists  between  all 
the  parts  of  the  series,  directly  between  the  alternate  plates 
of  the  different  cups,  and  indirectly  through  the  liquid  be- 
tween those  in  the  same  cup.  A  simple  circuit,  as  exhibited 
by  the  most  elementary  form  of  either  of  these  arrangements, 
represents  in  miniature  all  the  other  kinds  of  voltaic  apparatus 
employed.  Thus,  if  a  single  cup  be  used,  containing  a  plate 
of  zinc  and  one  of  copper,  immersed  in  dilute  acid,  and  having 
wires  attached  to  them,  the  voltaic  current  is  supposed  to 
be  developed  upon  the  surface  of  the  zinc,  along  with  its  par- 
tial solution  and  the  evolution  of  hydrogen,  to  pass  through 
the  liquid  to  the  copper,  and  to  be  conducted  through  that 


432 


WOLLASTON  S  BATTERY. 


metal  to  the  end  of  its  wire,  which  forms  the  anode  or  posi- 
tive pole.  The  end  of  the  wire  attached  to  the  zinc  is  the 
kathode  or  negative  pole.  When  these  poles  are  placed  in 
contact  with  each  other,  or  with  a  conductor  of  the  fluid,  the 
electricity  originally  developed  upon  the  surface  of  the  zinc 
returns  to  it  from  the  positive  wire  through  the  negative  one, 
and  if  the  current  be  sufiiciently  powerful,  the  various  phe- 
nomena of  voltaic  light,  heat,  electro-magnetism,  chemical 
decomposition  and  action  on  the  living  body,  are  capable  of 
being  exhibited  during  this  passage  from  pole  to  pole. 

In  most  of  the  forms  of  compound  circuits,  where  a  number 
of  pairs  of  plates  are  arranged  together  in  a  battery,  the 
wire  attached  to  the  terminal  zinc  plate  becomes  the  positive 
pole,  and  that  of  the  last  copper  plate  the  negative  one.  This 
arises  from  the  fact  that  in  these  arrangements  the  last  two 
plates  are  actually  superfluous,  not  being  so  much  producers 
of  the  galvanic  fluid,  as  conductors  of  that  which  has  been 
generated  in  the  intermediate  parts  of  the  apparatus. 

Our  limits  will  scarcely  permit  a  reference  even,  to  very 
many  of  either  the  theoretical  or  practical  points  connected 
with  the  phenomena  of  this  extensive  subject,  nor  does  it 
come  precisely  within  our  province  to  notice  the  former  at  all. 
We  will  therefore  confine  our  attention  to  the  construction 
and  uses  of  the  forms  of  voltaic  apparatus,  which  are  the  best 
known  and  the  most  used  in  the  laboratory  of  the  chemist. 

Fig.  386. 


WoUaston's  Battery, — This  is  the  very  best  of  the  old 


wollaston's  battery.  433 

forms  of  the  voltaic  battery.  It  consists,  as  shown  in  Fig.  386, 
of  a  number  of  zinc  and  copper  plates,  the  latter  entirely 
encircling  the  former  except  at  the  edges,  and  the  two  metals 
being  kept  apart  by  pieces  of  cork  or  wood.  Each  plate  of 
zinc  is  soldered  to  the  one  of  copper  which  is  before  it  in  the 
series,  and  the  whole  arrangement  is  screwed  to  a  bar  of  dry 
mahogany,  which  permits  its  elevation  from  or  depression 
into  the  acid.  This  is  contained  in  an  earthenware  trough, 
divided  by  partitions  into  compartments,  each  one  of  which 
receives  a  single  pair.  The  exciting  liquid  is  made  of  a  mix- 
ture of  100  parts  by  measure  of  water,  2 J  parts  of  sulphuric 
acid,  and  2  parts  of  strong  nitric  acid.  In  the  same  manner 
that  the  shock  of  the  Ley  den  jar  is  increased  by  combining 
it  with  others  in  a  battery,  the  power  of  this  apparatus  can 
be  multiplied  to  any  desired  extent,  by  uniting  it  by  means  of 
strips  of  copper,  passing  from  the  zinc  of  one  instrument  to 
the  copper  of  another,  with  any  desired  number  of  similar 
batteries. 

The  chief  objection  to  the  use  of  this  and  like  forms  of 
apparatus  is  what  is  called  the  local  action^  which  in  it  is  very 
great,  and  which  gives  rise  to  a  rapid  diminution  of  power 
and  corrosion  of  the  zinc. 

The  bubbles  of  hydrogen  given  off  from  its  surface,  adhere 
to  the  zinc,  preventing  perfect  contact  with  the  exciting  fluid ; 
some  of  the  electricity  is  dissipated  by  the  escaping  gas,  and 
the  sulphate  of  zinc  which  is  formed,  is  in  part  reduced  to  the 
metallic  state,  in  a  crust  upon  the  surface  of  the  copper.  All 
of  these  circumstances  form  serious  objections  to  the  use  of 
this  battery  where  a  long  continued  action  is  desired. 

When  common  zinc  is  exposed  to  dilute  sulphuric  acid,  it  is 
rapidly  dissolved,  and  this  solution  and  loss  of  material  in  the 
common  batteries  are  excessive  and  entirely  disproportional  to 
the  amount  of  galvanic  fluid  given  off'.  This,  which  is  the 
local  action,  is  supposed  to  arise  from  a  number  of  little 
voltaic  circles  being  formed  by  the  presence  in  the  zinc  of 
particles  of  plumbago,  and  of  other  metals  which  excite  the 
rapid  erosion  of  parts  of  its  surface.  This  evil  can  only  be 
prevented  by  carefully  amalgamating  the  surfaces  of  the  zinc 
plate. 

A  single  pair  of  Wollaston's  battery  is  very  efficient  in  the 
production  of  the  phenomena  which  are  due  to  the  evolution 
of  a  quantity  of  electricity,  such  as  ignition  and  deflagration 


434 


DANIELL  S  BATTERY. 


on  a  small  scale,  the  deflection  of  the  magnetic  needle  and 
the  various  electro-magnetic  experiments.  Its  intensity  or 
electro-chemical  power  is  very  much  increased  as  before  stated, 
by  combining  it  with  other  similar  arrangements. 

The  plates  of  the  old  form  of  voltaic  apparatus  should  be 
removed  from  the  acid,  and  washed  with  water  after  the  com- 
pletion of  each  experiment,  or  if  they  are  permanently  con- 
nected with  the  trough,  the  acid  in  it  should  be  poured 
out,  and  reserved  for  future  operations.  In  Wollaston's 
battery,  the  plates  are  taken  out  by  elevating  the  mahogany 
bar  to  which  they  are  attached,  are  freed  from  acid  and 
metallic  deposit  by  washing  with  water,  and  are  then  either 
suspended  over  the  trough  by  a  cord  attached  to  a  sup- 
port above,  or  are  placed  upon  a  tile  or  old  table  until  their 
next  employment.  As  the  acid  solution  soon  becomes  unfit 
for  use  from  the  large  amount  of  sulphate  of  zinc  dissolved 
in  it,  it  must  be  removed  after  reaching  a  certain  point  of 
saturation.  The  best  evidences  of  the  cleanliness  and  perfect 
connection  of  the  surfaces,  and  of  the  activity  of  the  liquor, 
are  afforded  by  the  constant  bubbling  up  of  hydrogen  during 
the  action,  and  by  the  ordinary  voltaic  phenomena  exhibited 
at  the  poles. 

DanielVs  Constant  Battery. — This  is  a  far  better  form  of 
apparatus  than  the  one  last  described,  and  has  the  advan- 
tage over  it  of  being  comparatively  permanent  in  its  action. 
The  local  action  being  obviated  by  the  amalgamation  of  the 
zinc,  it  is  of  course  much  more  applicable  to  those  purposes 
of  electro-chemical  examination  in  which  long  continued  and 
uniform  transmission  of  the  fluid  through  a  body  is  desired. 
In  its  simplest  form,  it  consists  of  a  copper 
cylinder  A,  3  or  4  inches  in  diameter,  and 
from  6  to  18  inches  in  height,  containing  in 
its  interior  a  cell  of  porous  earthenware  or 
of  animal  membrane,  within  which  is  sus- 
pended a  rod  of  zinc  three-quarters  of  an 
inch  in  diameter,  which  has  been  carefully 
amalgamated  by  rubbing  its  surface  with 
mercury  by  means  of  a  cloth  previously 
dipped  in  dilute  sulphuric  acid.  The  cell  or 
membrane  containing  the  zinc  is  filled  with  a 
mixture  of  one  part  by  measure  of  sulphuric 
acid  and  8  parts  of  water,  and  the  space  between  it  and  the 


Fig.  387. 


daniell's  battery.  435 

outer  copper  cylinder  contains  a  saturated  solution  of  sulphate 
of  copper,  the  surface  of  which  should  be  upon  the  same  level 
as  that  of  the  solution  within  the  cell.  The  solution  of  blue 
vitriol  is  prepared  by  pouring  boiling  water  over  an  excess  of 
crystals  of  the  salt,  and  stirring  constantly  until  it  is  satu- 
rated. 

To  this  solution,  a  little  sulphuric  acid,  never  amounting  to 
more  than  one-tenth  part  by  measure,  of  the  whole,  should  be 
added.  In  order  that  this  liquid  be  kept  concentrated,  a  lit- 
tle perforated  copper  shelf,  seen  in  the  figure,  is  usually 
placed  upon  the  inside  of  the  cylinder,  within  an  inch  or  two 
of  the  top.  This  is  intended  to  contain  a  supply  of  crystals  of 
the  sulphate.  They  are  placed  at  the  upper  part  of  the  liquid, 
because  that  portion  becomes  exhausted  first,  and  because  the 
saturated  solution  of  the  crystals  in  its  passage  downwards 
dilBfuses  itself  equably.  In  the  absence  of  the  shelf,  a  strong 
bag  of  loose  texture,  or  a  net-work  of  copper  wire  attached 
to  the  top  of  the  cylinder,  may  be  used  to  contain  the  crystals. 

Attached  to  each  metal  of  Daniell's  battery  is  a  binding 
screw  to  form  connections.  When  wires  are  held  in  each  of 
these,  and  a  communication  from  the  cylinder  to  the  rod  is 
made,  a  powerful  current  is  produced.  In  the  figure,  the  ex- 
tremity of  z  represents  the  positive  pole,  and  that  of  x  the 
negative  one.  In  this  arrangement  there  is  no  evolution  of 
hydrogen,  and  no  local  action  upon  the  zinc  or  consequent 
unnecessary  erosion  of  its  surface.  The  interior  of  the  copper 
cylinder  becomes  covered  with  a  compact  deposit  of  metallic 
copper  from  the  decomposition  of  the  oxide  by  the  nascent 
hydrogen. 

The  intensity  or  power  of  producing  electro-chemical  de- 
compositions of  this  battery,  may  be  much  increased  by  asso- 
ciating it  with  a  number  of  others.  Ten  pairs,  so  arranged 
that  the  inactive  metal  of  one  is  attached  by  copper  wires 
or  strips,  to  the  active  metal  or  the  zinc  of  the  next,  make  a 
most  powerful  compound  circuit,  quite  sufficient  for  nearly  all 
the  purposes  of  the  chemist. 

Daniell's  battery  may  be  constructed  very  simply  and 
cheaply,  by  immersing  in  a  tumbler  or  jar  containing  a  solu- 
tion of  sulphate  of  copper,  a  copper  plate  of  the  proper  size, 
bent  into  the  form  of  a  cylinder,  and  having  suspended  in  its 
centre  upon  a  piece  of  wood  supported  on  the  top  of  the  outer 
vessel — an  amalgamated  zinc  bar.     This  is  surrounded  by  a 


436 


smbe's  battery. 


piece  of  bladder  or  of  the  intestine  of  an  animal,  tied  at  its 
lower  part,  and  containing  the  acid  liquor.  Bags  of  very 
firm  sail  cloth,  well  sewn,  make  excellent  diaphragms  and  re- 
sist the  action  of  the  acid  for  a  long  time.  Cylinders  made 
by  cementing  coarse  strong  brown  paper,  at  the  edges  and 
bottom,  also  answer  perfectly  well.  The  terminal  wires  may 
be  soldered  upon  the  top  of  the  metals  with  which  they  are 
to  be  connected,  and  the  solution  of  sulphate  of  copper  may 
be  kept  saturated  by  the  means  before  spoken  of.  Very  little 
chemical  action  upon  the  surfaces  of  these  batteries  goes  on 
when  the  voltaic  circuit  is  not  completed:  nevertheless  it  is 
proper  always  to  pour  out  the  contents  of  the  diaphragm  or 
to  disconnect  the  zinc  bar  after  each  use  of  them.  The  liquid 
may  be  kept  in  a  separate  vessel,  and  employed  in  future 
experiments.  The  solution  in  the  outer  cylinder  may  be  al- 
lowed to  remain. 

Smees  Battery. — This  simple  and  powerful  apparatus  is 
chiefly  used  to  excite  the  precipitations  of  metals  in  the  Elec- 
trotype or  galvano-plastic  processes.  As  commonly  constructed 
and  shown  in  Fig.  388,  it  consists  of  two  plates  of  amalga- 
mated zinc,  clamped  to  a  piece  of  wood  by 
Fig.  388.  means  of  a  bent  strip  of  brass,  and  fur- 

nished with  a  binding  screw.  Between  the 
plates  of  zinc,  is  fixed  one  of  platinized  sil- 
ver, connected  at  its  upper  end  with  ano- 
ther similar  screw.  The  silver  is  covered 
o-ver  with  a  thin  layer  of  platinum,  by  first 
roughening  the  surface  with  strong  nitric 
acid,  and  after  washing,  placing  it  in  a 
vessel  of  water  acidulated  with  sulphuric 
acid,  to  which  a  little  chloride  of  platinum 
has  been  added.  A  porous  vessel  of  pipe- 
clay or  earthenware,  or  an  animal  mem- 
brane, with  a  plate  of  zinc  in  its  interior,  and  containing 
dilute  sulphuric  acid,  is  then  immersed  in  the  other  recepta- 
cle, and  the  silver  and  zinc  are  connected  together  by  a  wire. 
The  platinum  precipitates  upon  the  silver  surface  as  a  dark 
and  granular  but  closely  attached  deposite. 

This  rough  surface  of  the  silver  plate,  presenting  myriads 
of  minute  conducting  points,  greatly  facilitates  the  evolution 
of  hydrogen.  The  only  liquid  used  to  excite  this  battery 
consists  of  one  part  of  sulphuric  acid,  and  seven  of  water. 


groves'  battery.  437 

The  addition  of  a  few  drops  of  nitric  acid  makes  it  act  with 
greater  intensity,  but  it  is  not  advisable  to  use  it  unless  the 
silver  is  thoroughly  covered  with  platinum. 

Another  form  of  this  battery  consists  of  a  glass  vessel  like 
a  tumbler,  on  which  rests  the  frame  which  supports  the  me- 
tallic plates.  As  in  the  other,  two  screw  caps  on  the  top  of 
the  frame  allow  the  attachment  of  wires  for  the  conveyance 
of  the  current.  One  of  these  is  connected  with  a  central  slip 
of  platinum  foil,  on  each  side  of  which  descend  amalgamated 
zinc  plates,  connected  above  with  the  other  screw.  Like 
Daniell's  batteries,  a  series  of  these  may  be  connected  toge- 
ther, by  making  communication  between  the  alternate  zinc  and 
platinum  plates. 

G-roves'  Battery. — This  is  the  most  energetic  battery  known. 
Its  activity  is  very  great,  and  though  this  prevents  it  from 
being  so  well  adapted  for  galvanoplastic  operations,  it  is  the 
one  generally  employed  for  the  development  of  magnetism, 
and  is  in  common  use  in  the  magnetic  telegraph. 

Various  forms  of  this  arrangement  are  met  with,  but  in  the 
most  common  one,  a  strip  of  platinum  foil,  furnished  above 
with  a  screw  cap,  is  immersed  in  a  cylinder  of  porous  earthen- 
ware, filled  with  strong  and  pure  nitric  acid.  This  cylinder 
is  surrounded  by  another  one  of  amalgamated  zinc,  also  pro- 
vided with  a  screw  cap,  standing  on  short  legs,  and  divided 
by  a  longitudinal  opening  in  one  side,  in  order  to  permit  the 
acid  to  circulate  freely  around  it.  It  is  placed  in  a  glass  jar 
or  tumbler,  containing  one  part  by  measure  of  sulphuric  acid, 
and  eight  of  water.  When  the  circuit  is  completed  by  bring- 
ing together  the  wires  placed  in  the  screws,  the  hydrogen  from 
the  decomposed  water  in  the  outer  vessel  is  not  given  off  in 
the  gaseous  state,  but  passing  through  the  diaphragm,  com- 
bines with  some  of  the  oxygen  of  the  nitric  acid,  reducing  it 
to  nitric  oxide.  Some  of  this  dissolves  in  the  acid,  and  the 
rest  escapes  in  the  form  of  dense  red  fumes  of  nitrous  acid, 
formed  by  its  combination  with  the  oxygen  of  the  air. 

This  battery  owes  its  intensity  and  rapidity  of  action  to  the 
absorption  of  the  hydrogen,  the  good  conducting  nature  of  the 
materials,  and  the  consequent  concentration  of  the  fluid.  It 
has  been  said  to  be,  when  properly  prepared,  about  seventeen 
times  more  powerful  than  that  of  Daniell.  The  great  objec- 
tion to  its  use  arises  from  the  escape  of  the  irritating  and  poi- 


438 


bunsen's  battery. 


sonous  nitrous  acid,  which  is  sometimes  so  considerable  as  to 
fill  the  apartment  with  the  fumes. 

Bunsen's  Battery. — This  is  the  same  in  principle  as  Groves' 
battery,  but  is  more  economical,  as  a  cylinder  of  porous  coal 
is  used  in  place  of  platinum.     It  is  represented  in  Fig.  389. 

Fig.  389. 


A  B  is  a  glass  vessel  filled  up  to  B'  B'  with  commercial  nitric 
acid.  C  and  C  are  hollow  charcoal  cylinders,  dipping  into 
the  acid  as  far  as  B"  B'',  and  resting  on  the  edge  of  the  glass 
by  a  flange.  A  ring  of  zinc  or  copper  P  encircles  the  top  of 
the  charcoal  cylinder,  and  terminates  in  an  appendage  P',  for 
connecting  it  with  the  wire.  D  D,  which  are  diaphragms  of 
porous  earthenware,  contain  an  amalgamated  hollow  zinc 
cylinder  Z  Z,  with  its  appendage  P'^,  also  intended  for  com- 
munication, and  which  is  immersed  in  dilute  sulphuric  acid. 
The  connections  are  made  by  means  of  the  clamp  A  B,  Fig. 
390,  and  screw  V,  which  are  shown  in  place 
at  H,  Fig.  389.  The  perfect  contact  of 
these  appendages,  screws,  and  the  ribbons 
or  wires  of  copper  connected  with  them, 
Hiust  be  secured,  by  keeping  them  clean 
and  bright  by  rubbing  with  sand  paper. 
When  the  battery  is  about  to  be  used,  the 
glass  vessel  is  half  filled  with  equal  parts  of 
■commercial  nitric  acid  and  water,  and  the 
diaphragm,  with  water  acidulated  with  sulphuric  acid.  The 
coal  cylinder  is  prepared  by  pressing  a  thorough  mixture  of 


Fig.  390. 
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CONNECTION  OF  BATTERIES. 


439 


•+ 


one  part  of  caking  coal  and  two  of  coke  with  a  little  rye  flour, 
into  a  cylindrical  mould  of  sheet  iron,  in  the  centre  of  which 
is  a  core  of  wood  or  pasteboard.  The  mould,  after  being 
closed  by  a  movable  cover  well  luted  on,  is  heated  gradually 
to  redness,  and  the  calcination  is  continued  until  the  disen- 
gagement of  gas  ceases.  The  cylinder  is  then  taken  out, 
soaked  in  a  strong  solution  of  molasses,  dried,  and  again  cal- 
cined by  an  intense  heat,  in  order  to  increase  its  firmness  of 
texture.  After  this,  its^  surface  may  be  smoothed  off  with  a 
file,  or  in  a  lathe. 

This  battery  is  said  to  be  almost  equal  to  Groves'  in  power. 
Professor  Bird  has  constructed  one  similar  to  it  by  the  use  of 
a  black  lead  crucible.  He  ignited  the  crucible  for  a  short 
time,  and,  when  thus  prepared,  filled  it  with  nitric  acid,  and 
wound  a  wire  tightly  around  its  outside,  making  it  serve  both 
as  a  support  and  as  the  conductor  of  the  fluid.  A  bar  of 
amalgamated  zinc,  also  connected  with  a  wire,  was  then  placed 
in  a  porous  cylinder  containing  dilute  sulphuric  acid,  and  the 
whole  was  immersed  in  the  acid  of  the  crucible.  He  states, 
that,  although  powerful,  it  is  much  inferior  to  Groves'  bat- 
tery. 

In  the  use  of  any  of  the  above  described  batteries,  care 
must  be  taken  not  to  fill  either  of  the  receptacles  too  full  of 
the  liquid,  since  on  immersing  the  metals  or  charcoal,  some 
part  of  it  might  overflow  and  mix  with  that  of  the  other  ves- 
sel to  the  injury  of  the  surfaces.  After  the  insertion  of  the 
cylinders  or  bars,  the  surfaces  of  the  two  liquids  must  be  as 
nearly  as  possible  upon  the  same  level;  any  ^deficiency  in  this 
respect  being  compensated  by  the  addition  of  more  fluid. 

Connection  of  Batteries. — The  connection  between  the  dif- 

Fig.  391. 


440  WIRE  FOR  BATTERY  PURPOSES. 

ferent  plates  of  batteries  is  very  conveniently  made  by  means 
of  the  binding  screw,  Fig.  391.  The  wire  by  which  the  com- 
munication is  established,  is  passed  through  the  hole  in  the 
side,  and  kept  in  its  place  by  the  movable  screw  in  the  top. 
The  screw  below,  serves  to  fasten  the  arrangement  firmly  into 
a  hole  of  the  proper  size,  in  the  top  of  either  plate.  The 
operator  should  be  supplied  with  a  number  of  these,  as  they 
permit  him  to  unite  and  disconnect  the  different  parts  of  an 
apparatus  with  the  greatest  ease  and  rapidity.  They  are 
shown  in  the  figure,  attached  to  the  copper  and  zinc  plates  of 
a  simple  circuit,  with  the  wires,  of  which  the  ends  form  the 
poles,  passing  through  them. 

Wire  for  Battery  Purposes. — Copper  wire  is  more  often 
employed  for  connecting  the  different  parts  of  a  voltaic  cir- 
cuit than  any  other,  on  account  of  its  high  conducting  power, 
its  flexibility,  and  its  not  being  susceptible  of  magnetization 
by  the  passage  through  or  around  it,  of  a  galvanic  current. 
Its  thickness  should  be  proportioned  to  the  energy  of  the  bat- 
tery, and  it  should  be  as  short  as  possible,  because  a  great 
length  of  wire  causes  resistance  to,  and  loss  of  the  fluid  pro- 
ceeding from  a  battery  of  moderate  power.  Its  connecting 
parts,  as  well  as  those  of  the  plates  or  screws  to  which  it 
is  attached,  must  be  bright  and  clean.  In  order  to  ensure 
perfect  contact,  it  is  advisable  to  amalgamate  the  extremities 
of  the  wire.  This  is  readily  done  by  washing  them  with  a 
solution  of  nitrate  of  mercury,  and  dipping  them  afterwards 
in  metallic  mercury. 

This  coating  is  apt  to  oxidize,  and  thus  to  cause  an  inter- 
ference with  the  complete  connection.  When  this  occurs,  the 
film  of  oxide  is  to  be  rubbed  off,  and  the  amalgamated  surface 
renewed  as  before.  This  may  be  done  with  perhaps  greater 
ease  than  in  the  former  method,  by  placing  a  few  globules  of 
mercury  and  a  little  tallow  upon  a  piece  of  chamois  leather, 
and  then  rubbing  the  wire  with  it  until  the  mercury  adheres 
to  its  surface.  When  the  second  coating  is  applied  in  this 
way,  it  is  less  apt  to  become  tarnished  than  if  made  to  adhere 
by  the  aid  of  the  solution  of  the  nitrate.  When  it  is  desired 
to  break  and  renew  the  connections  often  or  very  rapidly,  the 
common  mode  of  attaching  the  wires  is  found  to  be  inconve- 
nient. In  that  case,  a  little  cup  made  of  copper,  or  other  metal 
which  does  not  too  readily  amalgamate  with  mercury,  is  partly 
filled  with  that  metal,  and  the  wires  are  received  in  the  cup,  a 


ELECTROLYSIS.  441 

depression  in  the  bottom  of  the  latter  being  often  made  so  as 
to  hold  them  more  firmly  in  their  place.  By  keeping  one  of 
the  wires  immersed  in  this  cup,  the  connection  may  be  made 
complete  or  broken  at  will,  and  without  disarranging  any  part 
of  the  apparatus,  by  simply  placing  the  extremity  of  the  other 
wire  in  its  appropriate  cup,  or  taking  it  out. 

The  wires  are,  in  one  point  of  view,  the  most  interesting 
parts  of  the  battery,  as  it  is  at  their  extremities  or  the  elec- 
trodes, that  the  most  important  phenomena  of  galvanism  are 
exhibited. 

Electrolysis. — Any  one  of  the  batteries  already  mentioned 
mJly  be  employed  for  the  purpose  of  producing  chemical  de- 
compositions, by  passing  the  current  from  them  through  the 
substance,  from  pole  to  pole  of  the  terminal  wires  of  the  series. 
As  electro-chemical  changes  are  usually  effected  most  per- 
fectly by  a  current  of  intensity,  as  distinguished  from  one  of 
quantity,  which  is  more  active  in  producing  light,  heat,  and 
electro-magnetism,  a  number  of  pairs  of  plates  or  cylinders, 
varying  with  the  difficulty  of  the  decomposition,  are  employed. 
The  other  results  spoken  of  are  generally  obtained  by  using 
a  small  number  of  plates  with  large  surfaces.  A  combination 
of  small  batteries,  made  upon  the  plan  of  Daniell's  is,  per- 
haps, the  most  active  of  all  in  producing  chemical  change. 

Whatever  form  of  apparatus  is  used  for  such  decomposi- 
tions, particular  attention  must  be  paid  to  the  proper  connec- 
tion of  the  alternate  metals,  and  to  the  close  contact  of  the 
wires,  as  well  as  the  other  circumstances  before  spoken  of  in 
reference  to  their  relative  size.  The  points  of  the  wires  should 
in  most  cases  be  made  of  platinum,  as  that  metal  is  the  best 
conductor  of  the  fluid,  and  is  not  liable  to  be  chemically  acted 
on  by  any  of  the  substances  evolved  from  the  electrolyte. 

Any  one  of  the  class  of  bodies  called  electrolytes,  which  in- 
cludes all  those  known  to  be  capable  of  decomposition  by  elec- 
tricity, may  be  exposed  to  the  voltaic  influence  by  being  placed 
between  the  electrodes  or  extremities  of  the  wires,  so  as  to  be 
the  medium  of  communication  between  them.  This  is  effected 
in  various  ways,  as  the  substances  differ  in  being  solid  or 
fluid,  and  good  or  bad  conductors  of  the  influence. 

Many  solutions,  like  that  of  iodide  of  potassium,  admit  very 

readily  of  decomposition.     A  solution   of  this  salt  may  be 

easily  decomposed  by  a  battery  consisting  only  of  a  wire  of 

zinc  and  one  of  copper.     Water  alone,  however,  may  require 

29 


442 


ELECTROLYSIS. 


the  power  of  a  number  of  cells  of  Daniell's  battery  to  separate 
it  into  its  elements.  The  addition  of  a  little  common  salt,  or 
of  almost  any  saline  body,  will  make  the  electrolysis  of  it 
much  more  easy  by  increasing  its  conducting  power. 

In  the  decomposition  of  water,  and  indeed,  in  most  cases 
in  which  gaseous  components  of  bodies  are  eliminated  from 
liquids,  platinum  strips  are  attached  to  the  ends  of  the  wires, 
thus  making  the  surfaces  of  contact  much  greater.  These 
strips,  which  may  be  made  of  platinum  foil,  are  placed  parallel, 
and  as  close  to  each  other  as  is  possible  without  their  being 
actually  in  contact.  Their  touching  each  other  would  eifect- 
ually  prevent  all  chemical  action,  as  the  voltaic  fluid  would  be 
directly  transmitted  through  the  wires  from  the  positive  to  the 
negative  plate. 

When  the  electrodes  are  placed  in  a  vessel  of  water,  and 
the  battery  is  made  to  act  properly,  bubbles  of  hydrogen  will 
ascend  from  the  end  of  the  wire  or  foil  connected  with  the 
negative  end,  and  oxygen  from  that  of  the  positive  one. 
These  gases  can  be  collected  in  a  tube  closed  at  one  end,  or 
ajar  previously  filled  with  water,  and  inverted  over  the  wires; 
or  they  may  be  separately  received  in  different  vessels.  As 
water  consists  of  two  volumes  of  hydrogen  and  one  of  oxygen, 
of  course  the  quantity  of  the  first  given  off,  will  be  twice  that 
of  the  last.     Fig.  392  represents  a  mode  of  effecting  this  de- 


Fig.  392. 


composition  in  which  the  terminal  wires  of  a  trough  arrange- 
ment, are  passed  through  a  perforated  cork  into  water  con- 
tained in  a  funnel.  The  end  of  each  wire  is  placed  directly 
under  a  test  tube  previously  filled  with  water,  and  inverted 


ELECTROLYSIS.  443 

in  the  funnel.     The  ascending  gases  displace  the  water,  oc- 
cupy the  tube,  and  may  if  necessary,  be  accurately  measured. 

As  the  quantity  of  electricity  set  in  motion  by  the  battery 
is  in  direct  proportion  to  the  amount  of  zinc  dissolved  in  it, 
so  are  the  effects  of  chemical  decomposition  always  proportion- 
ate to  the  former ;  this  being  thus  always  in  a  certain  rela- 
tion with  the  equivalents  both  of  the  products  of  electrolysis, 
and  of  the  portion  of  zinc  acted  upon.  Thus,  one  grain  of 
hydrogen,  given  off  at  the  negative  pole,  indicates  that  thirty- 
three  grains  of  zinc  have  been  dissolved  during  the  time  of 
the  action.  Upon  this  principle  Faraday  constructed  his  vol- 
tameter^ which  affords  the  only  means  known  of  accurately 
measuring  the  galvanic  influence.  That  form  of  this  which 
is  most  employed,  is  one  in  which  strips  of  platinum  foil  at- 
tached to  the  wires  of  a  battery,  are  placed  opposite  and  near 
to  each  other  in  a  jar  or  bottle,  from  which  a  tube  issuing, 
enters  under  a  graduated  jar  inverted  over  the  pneumatic 
trough,  all  of  these  vessels  being  full  of  water.  By  the  mea- 
sure of  the  gases  collected,  the  quantity  of  electric  force  can  be 
estimated.  By  placing  slips  of  platinum  upon  the  ends  of  the 
wires  in  Fig.  392,  and  substituting  a  single  graduated  tube 
with  a  wide  or  funnel-shaped  mouth,  for  the  two  which  are 
seen  in  the  cut,  the  same  result  may  be  attained. 

Faraday  describes  a  convenient  form  of  tube  for  the  collec- 
tion and  examination  of  gases  evolved  from  either  electrode, 
in  experiments  conducted  upon  a  small  scale.     This  tube,  re- 
presented in  Fig.  393,  is  filled  with  the  solution 
to  be  acted  upon,  and  held  in  the  position  re-         Fig.  393. 
presented.     The  nature  of  the  gas  to  be  col- 
lected, depends  on  the  end  of  the  battery  which 
is  fastened  to  the  curved  wire  at  a.     The  other 
electrode  is  to  be  loosely  inserted  at  6,  so  as  to 
allow  the  gas  given  off  from  it,  to  escape  through 
the  open  orifice.     It  should  not  be  placed  so 
far  within  the  extremity  of  the  tube  as  to  per- 
mit any  bubbles  of  the  gas  to  pass  around  the 
bend,  and  to  mix  with  that  in  the  upright  limb.         ^ 
The  wire  h  is  to  be  removed  when  a  sufficient 
amount  of  gas  has  been  collected,  and  the  latter  can  then  be 
transferred  to  a  suitable  vessel  and  examined. 

The  methods  of  subjecting  substances  to  the  action  of  the 
battery  are  very  numerous.     When  the  electrolyte  is  a  fluid, 


444  HEAT  AND  LIGHT  FROM  GALVANISM. 

it  may  be  placed  in  any  one  of  a  great  variety  of  suitable  re- 
ceptacles. In  all  cases  it  must  be  recollected  that  the  elec- 
trodes should  be  brought  as  near  together  as  possible,  so  that 
the  small  amount  of  the  substance  which  is  directly  between 
them,  shall  have  the  full  effect  of  the  current  concentrated 
upon  it.  Decompositions  of  a  drop  of  fluid  may  be  made  by 
placing  it  upon  a  glass  plate,  and  bringing  the  poles  in  con- 
tact with  its  sides.  Larger  quantities  may  be  received  in  a 
watch-glass  or  other  concave  piece  of  glass,  or  in  a  cup  of  the 
proper  size.  A  very  convenient  mode  of  subjecting  liquids  to 
the  current,  so  that  the  results  of  the  decomposition  can  be 
easily  inspected  by  the  observer,  is  that  of  closing  one  end  of 
a  piece  of  glass  tube  tightly  with  a  cork,  and  supporting  it  in 
an  upright  position  by  passing  one  of  the  wires  of  the  battery 
perpendicularly  through  the  cork.  The  tube  may  then  be 
filled  with  the  liquid,  and  the  other  wire,  bent  downwards,  may 
be  immersed  in  it,  and  placed  along  side  of  its  fellow.  In 
nearly  all  such  decompositions,  the  ends  of  the  poles  should 
be  armed  with  strips  of  platinum  foil,  on  account  of  the  greater 
surfaces  of  contact  presented  by  them. 

When  it  is  desired  to  direct  the  electrolytic  influence  upon 
a  large  surface  of  a  liquid,  a  piece  of  platinum  foil  attached 
to  one  pole  may  be  hollowed  out  into  a  cup-like  form,  and  the 
substance  may  be  placed  in  it;  or  the  terminal  wire  may  be 
made  to  support,  and  communicate  with  a  platinum  crucible, 
by  being  wound  around  it.  The  other  wire  can  then  be  im- 
mersed in  the  liquid,  and  prevented  from  touching  the  vessel 
by  the  intervention  of  a  piece  of  glass  tube. 

Production  of  Heat  and  Light  by  Galvanism. — The  phy- 
sical effects  of  galvanism,  among  which  are  the  production  of 
heat  and  light,  result  generally  from  the  passage  of  a  current 
of  great  quantity  and  of  feeble  intensity,  through  an  insuffi- 
cient or  imperfect  conductor,  the  resistance  of  the  latter  im- 
peding the  current,  and  increasing  its  calorific  power.  The 
batteries  employed  for  fusion  and  deflagration  generally  con- 
sist of  a  very  small  number  of  pairs  with  extensive  surfaces, 
which  will  develope  a  great  quantity  of  electricity.  Usually 
these  are  the  best  batteries  for  physical  experiments,  but  oc- 
casionally those  consisting  of  a  large  number  of  plates  are 
found  useful  for  such  purposes.  A  single  pair  of  very  mode- 
rate size  will  effect  these  results  in  a  small  way.  Thus,  Dr. 
Wollaston  fused  a  very  fine  wire  of  platinum  by  means  of  a 


HEAT  AND  LIGHT  FROM  GALVANISM.  445 

small  battery,  made  of  a  lady's  thimble  and  a  rod  of  zinc. 
We  have  before  stated  that  the  intensity  or  decomposing  power 
of  the  galvanic  fluid  is  increased  by  placing  batteries  in  con- 
nection so  as  to  multiply  the  number  of  plates.  Batteries 
may  also  be  associated  together  so  as  to  increase  their  calorific 
and  light  producing  power.  Any  number  of  troughs  like 
Wollaston's  may  for  this  purpose  be  placed — not  as  before, 
end  to  end — but  sidewise,  and  the  cells  at  either  end  of  each 
may  be  connected  with  the  same  cells  of  the  others  by  two 
wires,  going  across  the  series,  and  so  bent  as  to  be  in  perfect 
contact  with  the  last  plates.  The  projecting  ends  of  these 
wires  on  one  side  are  to  be  used  as  the  poles  of  the  battery. 

Daniell's,  or  any  other  of  the  cell  batteries,  can  be  made 
capable  of  producing  the  physical  phenomena  of  electricity, 
by  paying  attention  to  the  size  and  conducting  power  of  the 
wires  or  other  bodies  to  be  heated;  but  the  quantity  of  the 
fluid  is  much  increased  by  connecting  a  number  of  them  so  as 
to  make  them  equivalent  to  a  single  pair.  This  can  be  done 
by  connecting  together  all  the  copper  or  platinum  plates  by 
means  of  wires,  either  soldered  to  them  or  inserted  into  the 
binding  screws  already  spoken  of.  The  zinc  bars  or  cylinders 
are  to  be  brought  into  contact  in  like  manner,  and  the  poles 
may  be  made  by  attaching  wires  to  any  two  of  the  opposite 
pieces  of  metal. 

The  wires  of  such  batteries  should  all  be  made  of  larger 
size  than  those  which  are  employed  in  the  ordinary  arrange- 
ments. 

"When  the  electricity  developed  in  a  powerful  battery  is 
passed  through  conical  pieces  of  charcoal  placed  upon  its 
poles,  and  these  are  brought  into  contact,  and  then  withdrawn 
to  a  short  distance  from  each  other,  the  interval  becomes  oc- 
cupied with  a  brilliant  spark  or  arch  of  flame,  the  light  of 
which  is  often  too  vivid  to  be  borne  by  the  eyes.  The  heat 
given  out  is  also  very  intense,  and  gases  and  other  bodies  are 
sometimes  subjected  to  its  influence  for  the  purpose  of  being 
decomposed.  Carburetted  and  sulphuretted  hydrogen  are 
both  thus  aff*ected  by  it.  The  wires  may  be  twisted  around 
two  pieces  of  fine,  well-burnt  charcoal,  which  are  then  brought 
together.  The  brilliancy  of  the  spark  or  arch  passing  between 
the  points  of  charcoal,  serves  often  to  indicate  the  power  and 
good  condition  of  the  battery.  When  a  very  powerful  cur- 
rent is  set  in  motion,  it  is  advisable  not  to  make  the  contact 


446  hare's  sliding-rod  eudiometer. 

by  means  of  the  hands,  but  to  use  insulated  dischargers  analo- 
gous to  those  employed  in  electrical  experiments.  The  wires 
may  be  brought  together  and  disconnected  by  means  of  clamps 
or  small  vices  attached  to  wooden  handles.  These  may  be 
screwed  on  and  taken  off  at  pleasure.  The  charcoal  used  in 
these  experiments  must  be  of  the  best  quality.  It  is  properly 
prepared  by  packing  pieces  of  box  or  other  suitable  wood,  two 
inches  long,  and  a  quarter  of  an  inch  thick,  in  an  earthenware 
crucible,  and,  after  covering  them  up  with  dry  sand,  heating 
them  until  they  cease  to  flame.  The  best  pieces  must  be 
selected  and  preserved  for  use  in  a  well-stoppered  vessel. 

Various  substances  ignite  and  burn  with  brilliancy  between 
the  galvanic  poles.  Metallic  leaves  or  foil  of  different  kinds 
may  be  conveniently  burned  by  taking  them  up  upon  the  point 
of  one  electrode,  and  bringing  them  in  contact  with  a  plate 
of  polished  tinned  iron,  which  is  attached  to  the  other.  In 
this  way  the  different  appearances  and  colors  of  their  flames 
are  shown. 

A  platinum  wire  stretched  between  the  poles  of  a  battery, 
will  attain  a  red  or  white  heat,  and,  if  offering  sufficient  re- 
sistance to  the  passage  of  the  fluid,  may  even  be  fused.  It 
must  not  be  too  thin,  as  the  electricity  may  be  sometimes  so 
much  retarded  as  to  produce  no  visible  indications  of  heat. 
A  wire  of  the  proper  size  will  often  remain  at  a  red  heat  for 
a  great  length  of  time  if  a  constant  battery  is  used. 

The  power  possessed  by  the  battery  of  igniting  platinum 
wire,  enables  us  to  apply  heat  in  situations  in  which  it  would 
be  difficult  or  impossible  to  do  it  by  other  means.  By  its 
use,  substances  placed  under  water  may  be  ignited  or  exploded, 
if  necessary,  at  a  great  distance  from  the  operator.  Out  of 
the  laboratory,  it  may  be  employed  for  the  purpose  of  ex- 
ploding gunpowder  in  mines,  or  under  ships,  and  in  other  posi- 
tions far  removed  from  the  source  of  electricity;  while,  in  it, 
it  may  be  used  for  the  explosive  decomposition  of  various 
gases. 

Dr.  Hare  has  taken  advantage  of  this  power  in  the  con- 
struction of  his  sliding-rod  aqueous  eudiometer.  This  instru- 
ment consists  of  a  glass  vessel,  with  a  capillary  orifice  closed 
by  a  spring  and  lever  in  its  top,  and  connected  below  with 
a  socket,  and  a  tube  in  which  a  graduated  piston  moves.  A 
fine  wire  of  platinum  is  stretched  across  the  middle  of  the 
vessel,  between  two  brass  wires,  which  pass  through  the  socket 


hare's  calorimotor.  447 

below,  and  terminate  in  legs,  which  are  made  capable  of  con- 
nection with  the  cups  upon  the  poles  of  a  battery.  The  instru- 
ment having  been  filled  with  water,  the  gaseous  mixture  is 
drawn  into  it  in  the  proper  quantities  by  pulling  out  the  pis- 
ton to  regulated  distances,  and  is  then  exploded  by  the  igni- 
tion of  the  wire,  after  the  capillary  orifice  has  been  closed. 
This  last  is  now  again  opened,  but  under  water,  enough  of 
which  enters  to  supply  the  vacuum  produced  by  the  condensa- 
tion. The  amount  of  undecomposed  air  which  remains,  is 
indicated  by  the  distance  through  which  the  rod  has  to  be 
passed  for  the  purpose  of  expelling  it  all  from  the  glass 
vessel. 

Dr.  Hare  uses  for  the  ignition  of  the  wire  in  this  experiment, 
his  calorimotor  of  two  pairs  of  plates.  He  has  constructed  a 
variety  of  arrangements  for  procuring  the  heating  efi^ects  of 
the  battery.  In  one  of  these,  twenty  sheets  of  copper,  and 
the  same  number  of  zinc  plates,  united  separately  to  two  bars 
of  metal,  were  secured  in  a  wooden  frame,  so  as  to  leave  a 
space  between  them  of  a  quarter  of  an  inch.  A  rope  passing 
over  a  pulley,  was  attached  at  one  end  to  the  frame,  and  at  the 
other  to  a  counterpoising  weight.  The  frame  could  be  lowered 
by  means  of  the  rope  into  a  cubical  box  containing  the  acid 
liquor.  Another  form  of  Hare's  battery  is  so  constructed 
that  the  vessel  containing  the  acid  is  raised  up  to  and  lowered 
from  the  plates,  when  necessary,  by  means  of  a  lever  connected 
with  pulleys.  By  this  most  convenient  and  powerful  battery, 
constructed  with  a  new  arrangement  of  the  plates,  the  most 
intense  galvano-ignition  and  deflagration  may  be  accom- 
plished. 

This  apparatus,  the  description  of  which  might,  perhaps, 
have  been  more  properly  introduced  along  with  the  account 
of  other  batteries,  is  shown  in  Figs.  394  and  395.  We  ex- 
tract the  description  of  it  from  Hare's  Compendium. 

"  The  two  forms  of  calorimotor  represented  by  Figs.  394 
and  395,  have  been  much  used  by  me  for  what  is  described 
in  my  Compendium  as  "•  galvano-ignition. ''  (C,  335.)  Within 
any  cavity,  ignition  of  any  intensity  short  of  fusing  platina 
may  be  produced,  by  making  a  platina  wire  the  subject  of  a 
galvanic  discharge  from  an  instrument  of  this  kind.  I  first 
resorted  to  this  process  in  the  year  1820,  for  the  purpose  of 
igniting  gaseous  mixtures  in  eudiometers  of  various  forms. 
In  June,  1831, 1  applied  it  to  ignite  gunpowder  in  rock  blast- 


448 


HARE  S  CALORIMOTOR. 


ing;  and  to  this  object  it  was  subsequently  applied,  agreea- 
bly to  my  recommendation,  by  Colonel  Pasley,  Professor 
O'Shognessy,  and  others. 

Fig.  394. 


"  This  machine  consists  of  sixteen  plates  of  zinc,  and  twenty 
plates  of  copper,  each  twelve  inches  by  seven,  arranged  in 
four  galvanic  pairs.  The  plates  are  supported  within  a  box 
with  a  central  partition  of  wood,  A  B,  dividing  it  into  two 
compartments.  Each  of  these  may  be  considered  as  separated 
into  two  subdivisions,  by  four  plates  of  copper  between  the 
letters  C  C.  Of  course  the  box  may  be  considered  as  com- 
prising four  distinct  spaces.  No.  1,  No.  2,  No.  3,  and  No.  4. 
The  circuit  is  established  in  the  following  manner.     Between 


THE  GALVANOMETER.  449 

the  zinc  plates  af  compartment  No.  1,  and  the  copper  plates 
of  compartment  No.  2,  a  metallic  communication  is  produced, 
by  soldering  their  neighbouring  corners  to  a  common  mass  of 
solder,  with  which  a  groove  in  the  wooden  partition  between 
them  is  filled.  With  similar  masses  of  solder,  two  grooves 
severally  made  in  the  upper  edges  of  each  end  of  the  box  are 
supplied.  To  one  of  them,  the  corners  of  all  the  copper  plates 
of  space  No.  1,  and  the  zinc  of  space  No.  4,  are  soldered.  To 
the  other,  the  zinc  plates  of  space  No.  2,  and  the  copper  plates 
of  space  No.  3,  are  soldered  in  like  manner.  Lastly,  the  zinc 
plates  of  No.  3  are  connected  by  solder  in  a  groove,  and  the 
copper  plates  of  No.  4  are  in  like  manner  connected  by  solder 
in  another  groove.  Upon  the  ends,  SS,  of  the  solder  just 
mentioned,  the  gallows  screws  are  severally  soldered,  and  to 
these  the  rods,  P  P,  called  poles,  are  fastened.  The  means  by 
which  the  acid  is  made  to  act  upon  the  plates  must  be  suffi- 
ciently evident  from  inspection.  Depressing  the  handle  causes 
the  wheels  to  revolve,  and  thus,  by  means  of  the  cord  which 
works  in  their  grooved  circumferences,  to  lift  the  receptacle 
which  holds  the  acid,  until  this  occupies  the  interstices  between 
the  plates." 

Means  of  Detecting  the  Galvanic  Fluid. — The  Galvano- 
meter.— If  a  common  magnetic  needle,  supported  upon  its 
pivot,  be  placed  directly  under  and  parallel  to  a  wire  which 
is  connected  with  the  poles  of  a  galvanic  circuit,  so  that  the 
positive  fluid  will  pass  through  the  wire  from  the  north  to  the 
south,  it  will,  during  the  passage  of  the  current,  leave  its  po- 
sition in  the  magnetic  meridian,  and,  after  a  few  oscillations, 
assume  one  nearly  or  quite  at  right  angles  to  it,  its  northern  end 
or  austral  pole  pointing  to  the  east,  or  to  some  point  between  it 
and  the  north.  Precisely  the  same  eflect  will  be  produced  if 
the  needle  is  placed  over  the  wire,  and  if  the  direction  of  the 
current  is  reversed.  But  the  northern  end  will  be  turned  to- 
wards the  west,  if  the  current  is  passed  from  the  north  to  the 
south  while  the  wire  is  under  it,  and  also  in  the  same  direction 
if  the  wire  again  placed  over  it,  transmits  the  fluid  from  the 
south  to  the  north.  The  needle  always  returns  to  its  former 
position  immediately  after  disconnecting  the  wire.  The  power 
possessed  by  a  galvanic  current  of  influencing  the  magnet, 
may  be  increased  to  almost  any  extent,  by  passing  it  through 
a  number  of  wires,  or  a  coil  made  of  a  single  one,  so  as  to  make 
the  action  of  the  whole  equivalent  to  the  sum  of  the  actions 


450  THE  GALVANOMETER. 

of  all  its  spires.  This  can  be  done  most  effectually  by  bend- 
ing a  long  wire,  covered  with  cotton  or  silk  to  prevent  the 
lateral  escape  of  the  current,  into  the  form  of  a  rectangle. 
The  needle  is  supported  parallel  to,  and  between  its  horizon- 
tal branches,  and  it  is  obvious  that  it  will  be  similarly  affected 
by  each  part  of  the  coil,  in  whatever  position  its  wires  may  be ; 
for,  as  before  stated,  a  current  passing  above  it  from  the  north 
to  the  south,  and  one  passing  below  from  the  south  to  the 
north,  cause  it  to  deflect  in  the  same  direction.  This  instru- 
ment is  the  galvanometer,  or  the  ''  electro-magnetic  multiplier' 
of  Schweigger.  By  its  use  we  can  detect  traces  of  electricity 
much  too  minute  to  act  on  the  gold-leaf  electrometer;  but  its 
chief  applications  are  to  the  discovery  of  delicate  galvanic 
currents,  and  to  the  determination  of  their  direction.     As 

Fig.  396. 


shown  in  the  figure,  it  consists  of  the  coil  of  covered  copper 
wireNBS,  containing  usually  about  twenty  convolutions,  of 
which  the  extremities  are  connected  with  the  cups  C  Z.  A 
card  graduated  into  360°  is  fixed  to  the  board  A,  so  that  a 
line  drawn  between  the  numbers  360  and  180,  coincides  with 
the  direction  of  the  centre  of  the  coil.  Above  this  is  placed 
a  delicate  magnetic  needle,  supported  on  a  pivot.  The  coil 
is  placed  with  its  long  axis  in  the  magnetic  meredian.  If  any 
source  of  feeble  electricity  is  now  connected  with  the  cups, 
the  current  from  it  will  pass  through  the  coil,  and  the  magnet 
will  move  to  the  east  or  west,  according  to  the  direction  of 
the  fluid.  The  intensity  of  the  influence  is  estimated  in  de- 
grees, by  comparing  the  position  of  the  utmost  divergence  of 
the  needle  with  the  number  under  it  on  the  card.  The  deli- 
cacy of  this  instrument  depends  in  a  great  measure  upon  the 
number  of  convolutions  of  wire.  Thus,  if  all  other  circum- 
stances are  favourable,  it  may  be  supposed  that  one  consisting 
of  one  hundred  turns  will  detect  an  amount  of  electricity 
which  is  only  one-fifth  as  great  as  that  shown  by  the  one  with 
twenty  convolutions. 


THE  ASTATIC  GALVANOMETER. 


451 


The  Astatic  G-alvanometer. — The  sensibility  of  the  common 
galvanoscope  may  be  almost  indefinitely  increased  by  connect- 
ing the  magnetic  needle  immovably  with  another  one  placed 
above  the  rectangular  coil  of  wire,  but  parallel,  and  opposed 
in  the  direction  of  its  poles  to  the  first.  They  are  fastened 
by  their  centres  to  a  common  axis,  which  revolves  freely  in 
an  aperture  of  the  upper  branch  of  the  coil.  This  axis  is  sus- 
pended by  a  fibre  of  silk  to  the  upper  part  of  the  glass  or 
other  vessel  in  which  the  whole  is  encased,  and  it  penetrates 
a  graduated  card,  placed  under  the  upper  needle.  This  ar- 
rangement makes  the  needle  a  balance  of  torsion,  the  move- 
ments of  which  are  compared  with  the  degrees  marked  upon 
the  card,  in  the  same  way  as  in  the  simple  multiplier.  Ter- 
restrial magnetism  has  scarcely  any  effect  upon  this  system  of 
needles,  and  would  have  none  at  all  if  both  possessed  an  equal 
amount  of  magnetic  power,  the  tendency  of  the  one  to  assume 
its  position  in  the  meridian  being  in  that  case  entirely  coun- 
teracted by  the  reversed  direction  of  the  other.  By  a  refer- 
ence to  the  statements  at  the  head  of  this  article,  it  will  be 
seen  that  a  current  passed  through  the  coil,  in  either  direc- 
tion, will  have  the  same  efi'ect  upon  both  needles.     Fig.  397 

Fig.  397. 


represents  two  of  the  many  forms  of  Nobili's  galvanometer. 
It  is  called  astatic  because  it  is  unafi'ected,  or  nearly  so,  by 
the  magnetism  of  the  earth. 

As  these  instruments  are  used  not  only  to  detect  currents, 
but  also  to  ascertain  the  directions  in  which  they  pass  through 


452  CONSTRUCTION  OF  FORMULAE. 

the  wires,  it  is  of  importance  to  impress  upon  the  mind  the 
movements  of  the  needles  which  indicate  that  one  or  other 
extremities  of  the  coil  are  in  connection  with  the  positive  or 
negative  electric  poles.  A  simple  aid  to  the  memory  is  to 
suppose  that  a  current  is  passing  around  the  middle  of  a 
watch,  from  the  handle  over  the  face,  and  is  returning  back 
to  its  place  of  origin.  The  minute  hand,  if  pointing  to  the 
hour  twelve,  which  is  usually  placed  next  to  the  handle,  may 
be  supposed  to  represent  the  northern  half  of  the  needle. 
It  would  then  move  around  in  its  usual  direction  towards 
the  figure  three.  If  the  current  were  passed  around  the 
back  of  the  watch  from  the  handle,  and  returned  to  the  face, 
the  hand  would  move  backwards  towards  the  figure  nine. 
Ampere  has  devised  the  following  formula,  which  is  still  better 
calculated  to  impress  the  direction  of  the  deviations  upon  the 
memory.  "  Let  any  one  identify  himself  with  the  current,  or 
let  him  suppose  himself  to  be  lying  in  the  direction  of  the 
positive  current,  his  head  representing  the  copper,  and  his  feet 
the  zinc  plate,  and  looking  at  the  needle,  its  north  pole  will 
always  move  towards  the  right  hand."  The  person  must, 
however,  suppose  himself  to  be  lying  over  the  needle,  his  head 
and  its  north  pole  being  both  in  the  same  direction. 

Our  limits  would  not  permit  us  to  refer  to  the  applications 
of  galvanism  to  electro-magnetic  apparatus,  or  the  electrotype, 
even  if  these  were  more  pertinent  than  they  are  to  our  sub- 
ject. A  full  account  of  them  is  to  be  found  in  a  number  of 
popular  treatises.  ''Davis  Manual  of  Magnetism,''  and 
Walker's  ''Electrotype  Manipulations,''  contain  a  full  de- 
scription of  all  the  means  employed  in  experiments  on  these 
subjects,  and  of  their  practical  applications. 


CHAPTER   XXXI. 

CONSTRUCTION  OF  FORMULA. 

All  compounds  are  either  mechanical  mixtures  following  no 
precise  law,  or  consist  of  simpler  bodies  united  in  definite  pro- 
portions agreeably  to  the  laws  of  chemical  attraction.  The 
latter  may  be  represented  by  formulae. 


CONSTRUCTION  OF  FORMULA..  453 

There  are  many  advantages  attending  the  employment  of 
formulae,  and  nothing  has  tended  to  advance  the  science  of 
chemistry  further  and  more  rapidly  than  their  use.  They 
convey  to  the  eye,  like  pictures,  a  far  clearer  view  of  the 
nature  of  a  compound  than  the  most  labored  description  could 
eiFect.  While  they  are  established  by  analysis,  their  reaction 
tends  to  confirm  or  disprove  its  results.  As  they  are  pic- 
torial representations,  the  memory  may  retain  the  composition 
of  thousands  of  compounds,  and  yet  not  be  overburdened. 
Isomorphous  bases  may  be  thrown  together  under  a  short  and 
general  expression,  and  thus  substances,  often  differing  widely 
in  external  properties,  are  brought  into  natural  groups,  a  re- 
sult to  which  the  analysis  of  a  body  would  never  lead  without 
the  formula. 

When  a  definite  compound  has  been  separated  by  analysis 
into  its  constituent  parts,  their  relative  proportion  is  generally 
expressed  in  per  centages,  but  such  a  mode  of  expression  does 
not  convey  a  clear  idea  of  the  chemical  nature  of  the  body,  as 
compared  with  other  compounds,  containing  the  same  or 
allied  constituents.  The  per  centage  composition  is  usually 
given  as  simply  expressing  the  results  of  analysis.  To  ascer- 
tain the  nature  of  the  union  among  the  constituents,  agree- 
ably to  the  received  laws  of  affinity,  they  must  be  reduced 
from  their  per  centage  proportion  to  the  proportions  of  their 
equivalents.  If  any  one  of  the  constituents  happens  to 
express  in  the  per  centage  results,  the  combining  weight  of 
that  body,  the  others  will  also  express  their  combining  weights 
or  multiples  of  them.  Or  if  any  one  can  be  multiplied  or 
divided  by  any  number,  which  will  give  the  combining  weight 
of  that  body,  the  others  multiplied  or  divided  by  the  same 
number,  (in  order  to  keep  up  the  same  proportion  as  in  the 
per  centage  results,)  will  express  their  combining  weight  or 
multiples  of  them. 

Thus  the  analysis  of  carbonate  of  lime,  according  to 
Dumas  (1),  and  Erdman  and  Marchand(2),  gives — 

1  2  -4-2 

Lime  56.06  56  28 

Carbonic  acid  43.94  44  22 


100.00  100  50 

If  the  44  carbonic  acid  be  divided  by  2,  it  gives  the  com- 
bining weight  of  one  equiv.  of  the  acid ;  and  the  lime  if  divided 


454  CONSTRUCTION  OF  FORMULA. 

also  by  2,  gives  the  combining  weight  of  one  equiv.  of  it.  It  is, 
therefore,  composed  of  1  equiv.  of  each  constituent.  Again, 
if  b6  be  divided  by  the  combining  weight  of  lime,  28,  the  re- 
sult is  2 ;  and  44  divided  by  the  combining  weight  of  the  acid, 
likewise  gives  2.  The  proportion  between  the  equivs.  is, 
therefore,  2  :  2 ,  or  reduced  to  the  lowest  term  1  :  1. 

Now  since  the  per  centage  composition  expresses  the  pro- 
portion between  the  combining  weights  of  the  constituents, 
if  each  constituent  be  divided  by  its  combining  weight,  the 
result  will  be  the  proportion  between  the  number  of  equiva- 
lents in  the  compound. 

Then  the  lowest  of  these  numbers  divided  by  itself  gives 
unity ;  and  the  others  divided  by  the  same  number  will  express 
the  proportion  between  all  the  equivalents,  and  generally  in 
whole  numbers,  if  the  analysis  has  been  correct.  Thus  the  ana- 
lysis of  blue  vitriol,  by  Berzelius,  gives  the  following  numbers 
in  the  1st  column,  expressed  in  100  parts. 

Oxide  of  copper        32.13         0.803  1.018         1 

Sulphuric  acid  31.57         0.789  1.000         1 

Water  36.30         4.0333         5.111         5 

The  constituents  being  severally  divided  by  their  combining 
weights,  the  numbers  in  the  2d  column  result ;  and  by  dividing 
each  of  these  by  0.789,  we  get  the  3d  column,  which,  by 
making  a  slight  allowance  for  the  imperfections  of  analysis, 
gives  the  proportions  between  the  equivalents  1:1:5. 

Having  determined  the  number  of  equivalents,  a  formula  is 
easily  established,  which  in  the  case  of  carbonate  of  lime  is 
CaO,C02,  and  of  blue  vitriol  CuO,S034-5HO.  Now  the  per 
centage  composition  of  dry  or  anhydrous  sulphate  of  copper 
is  50  oxide  of  copper  and  50  sulphuric  acid.  If  we  compare 
it  with  the  per  centage  composition  of  blue  vitriol,  the  relation 
between  them  is  not  readily  seen ;  and  in  the  case  of  many 
other  substances,  no  relation  whatever  can  be  detected;  but 
if  the  formulae  deduced  from  each  analysis  be  compared,  their 
relation  is  at  once  evident,  for  we  perceive  that  the  blue 
vitriol  contains  5  equivalents  of  water,  which  the  other  does 
not,  and  that  otherwise  they  are  one  and  the  same  substance. 

The  silicates  form  a  numerous  class  of  crystallized  minerals, 
whose  formula  may  be  established  by  the  foregoing  method, 
or  by  determining  the  quantity  of  oxygen  in  each  element, 
and  bringing  these  quantities  into  whole  numbers,  those  of 
the  isomorphic  bases  being  added  together.     It  is,  perhaps,  a 


CONSTRUCTION  OF  FORMULAE. — GLASS-BLOWING.         455 

more  convenient  method  for  these  bodies  than  the  preceding. 
The  construction  of  the  formula  for  an  organic  body  depends 
on  precisely  the  same  principles,  and  is  ascertained  by  a 
similar  process ;  but  there  is  a  peculiarity  in  the  formula  of 
organic  bodies,  which  is  rarely  met  with  in  mineral  substances. 
Thus  the  analysis  of  defiant  gas  gives  as  its  formula  CH ;  but 
from  its  density  and  other  circumstances  it  should  be  C2H2  or 
C4H4.  The  formula  deduced  from  the  analysis  of  sugar  is 
CHO,  but  it  decomposes  into  alcohol  and  carbonic  acid,  and, 
therefore,  either  C2H30  +  C02=C3H303  ought  to  be  the  for- 
mula, or  CgHgOg  or  C^fi^fi^^y  which  last,  indeed,  is  most  gene- 
rally received.  A  formula  may  also  be  doubled,  or  trebled, 
if  viewed  as  a  bibasic  or  tribasic  acid.  Therefore,  after  de- 
termining the  simplest  formula  for  an  organic  body,  its  more 
rational  formula  is  determined  by  the  specific  gravity  of  its 
vapor,  by  its  mode  of  combining  with  bases  or  acids,  or  by 
its  metamorphoses. 


CHAPTER  XXXII. 

GLASS-BLOWING. 

The  ability  to  work  glass  over  the  lamp  or  blowpipe-flame 
is  a  very  desirable  accomplishment  for  the  chemist,  as  it  ena- 
bles him  to  fashion  for  himself,  and  in  accordance  with  his 
own  judgment,  such  micro-apparatus  as  is  constantly  in  de- 
mand during  experimental  research.  The  inconvenience  and 
expense  of  having  a  large  stock  of  delicate  glass  instruments 
always  at  hand,  and  the  difficulty  of  obtaining  such  at  all 
times,  especially  in  localities  distant  from  the  cities,  render 
instruction  in  the  art  doubly  desirable.  On  these  accounts, 
we  think  it  proper  to  devote  a  chapter  to  a  few  illustrations 
of  the  processes  by  which  tubes  are  bent,  closed,  rounded, 
widened,  and  drawn  out,  and  by  which  bulbs  are  blown  and 
joints  sealed. 

The  two  principal  pieces  of  apparatus  required  are  a  lamp 
and  a  table  blowpipe.  The  latter,  as  well  as  its  management, 
have  already  been  written  of  at  page  59.     The  former,  known 


456 


DANGER  S  GLASS-BLOWER  S  IMPROVED  LAMP. 


as  Danger's  "glass-blower's  improved  lamp,"  of  form  shown 
by  Fig.  398,  is  of  sheet  brass,  and  rests  upon  a  tray  designed 

Fig.  398. 


for  the  reception  of  any  overflow  of  oil.  These  lamps  are 
fitted  with  an  arrangement  by  which  the  wick  may  be  raised 
or  lowered,  and  the  flame  consequently  enlarged  or  diminished 
as  desired:  an  accompanying  hood,  serves  to  increase  the 
heat  and  to  protect  the  eyes  from  the  smoke  and  flame. 

The  wick  may  be  made  of  common  candle  wick,  divided 
into  lengths  of  proper  dimensions,  and  stranded  together,  so 
as  to  form  a  diameter  of  about  three-fourths  of  an  inch.  This 
bunch  is  placed  in  that  part  of  the  lamp  intended  as  its  re- 
ceptacle, and  should  only  protrude  above  the  oil  about  the 
third  of  an  inch.  When  it  is  desired  to  lessen  the  power  of 
its  flame,  as  may  be  necessary  in  the  heating  of  small  tubes, 
the  force  of  the  blast  can  be  diminished  so  as  to  make  the 
flame  of  the  desired  height  and  intensity. 

The  fuel  may  be  olive,  lard,  sperm,  or  tallow  oil ; — the  latter, 
however,  being  preferable  on  account  of  its  giving  a  hotter 
flame.  In  case  of  the  absence  of  a  lamp  of  this  sort,  any 
common  metallic  vessel,  of  proper  size,  may  be  fitted  for  use, 
upon  the  blowpipe  table,  by  training  up  upon,  and  allowing 
to  overhang  its  side,  a  thick  bunch  of  wick.  This  may  be 
kept  in  place,  and  its  flame,  at  the  same  time,  be  prevented 
from  descending  too  far,  by  encircling  it  with  a  tin  or  other 
metallic  tube,  or  a  coil  of  wire,  which  may  be  temporarily 
connected  with  the  sides  of  the  vessel,  so  as  to  answer  all  the 
intentions  of  support  and  the  conduction  off*  of  the  excess  of 
heat. 


S 


GLASS-BLOWING  : — THE  TABLE.  457 

If  the  experimenter  cannot  have  accefes  to  a  properly  made 
blowpipe  table,  he  may,  in  a  very  short  time,  construct  a  sub- 
stitute himself,  which,  however  rough,  will  enable  him  to  carry 
on  nearly  all  the  operations  of  glass-blowing.  A  hollow  reed 
or  piece  of  cane  angle,  about  a  foot  in  length,  may  be  firmly 
fixed  in  a  circular  hole,  drilled  near  the  edge  of  a  common 
table,  and  which  is  just  large  enough  to  admit  and  hold  it 
firmly  in  its  place.  This  may  have  adapted,  by  means  of 
cement,  plaster  or  putty,  to  its  upper  end,  a  nozzle  of  metal,  or 
of  glass  drawn  out  to  the  proper  sized  orifice,  or  one  made  of 
a  piece  of  tobacco  pipe  of  the  requisite  calibre.  A  bladder 
of  the  largest  size,  or  bag  of  caoutchouc,  furnished  with  two 
openings  upon  the  same  part  of  its  circumference,  is  now 
firmly  attached  to  the  bottom  of  this  tube,  by  one  of  these  a 
similar  piece  of  reed,  long  enough,  however,  to  reach  from  the 
operator's  knees — while  sitting — to  his  mouth,  having  been 
inserted  and  tied  into  the  other  opening.  That  end,  of  this 
last-mentioned  tube,  which  is  within  the  bladder,  should  be 
provided  with  a  valve,  like  that  of  a  cupping  glass,  made  by 
placing,  loosely  over  it,  a  long  strip  of  oiled  silk  of  the  dia- 
meter of  the  tube,  folding  the  ends  upon  the  body  of  the  reed 
and  tying  them  firmly  to  it  by  waxed  thread.  This  valve 
admits  of  the  passage  of  air  into  the  receptacle,  but  will  not 
allow  its  return  through  the  same  orifice,  so  that  pressure 
upon  the  bladder  will  compel  its  exit  through  the  nozzle  of 
the  tube  which  is  fixed  in  the  table.  If  now  the  operator, 
sitting  near  the  table  with  the  bladder  hanging  between  his 
knees  and  the  loose  tube  fixed  in  his  mouth,  inflates  the 
former,  and  then  presses  upon  it  uniformly  with  his  knees,  a 
continuous  current  is  expelled  from  the  nozzle  upon  the  flame 
of  the  wick  placed  directly  above  it.  A  repetition  of  the 
inflation  only  becomes  necessary  when  the  bladder  is  nearly 
emptied  of  its  contained  air.  The  inflation  of  this  home- 
made apparatus  is  scarcely,  if  at  all,  fatiguing,  and  it  per- 
mits to  the  glass-blower  the  unincumbered  use  of  both  his 
hands. 

The  position  of  the  jet  upon  the  top  of  the  table,  and 
that  of  the  operator  before  it,  are  shown  in  the  annexed 
drawing. 

When  it  is  desired  to  use  the  gas  flame,  which  is,  however, 
not  so  good  as  that  of  oil,  the  straight  jet  and  Argand  burner, 
as  is  shown  in  the  above  drawing,  are  employed.     It  is  still 
30 


458 


GLASS-BLOWING  :   IMPLEMENTS. 


better,  in  ordering  a  blast  table,  to  have  prepared  a  jet,  with 
ball  and  socket  joint  suitable  to  either  kind  of  flame,  and 

Fig.  399. 


^   \  W  V 


which  can  be   screwed  to,  or  removed  from,  the  table  at 
pleasure. 

The  other  implements  are  an  iron  piercer  with  wooden 
handle.  Fig.  400,  a  cone  of  biscuit-ware.  Fig.  401,  for  widen- 


Fig.  400. 


Fig.  401. 


Fig.  402. 


ing  the  necks  of  tubes,  a  small  pair  of  brass  tongs,  Fig.  402, 
for  fashioning  bulbs,  &c.,  a  small  piece  of  smooth  hoop-iron. 


CUTTING  OF  GLASS.  459 

styled  the  marver,  a  hardened  cast-steel  knife,  and  one  or  two 
three-cornered  files  for  cutting  tubes  and  rods. 

In  addition  to  the  above,  the  table  should  be  supplied  with 
a  stock  of  tubes  and  rods,  of  assorted  diameters,  and  made  of 
glass  free  from  lead.  They  should,  moreover,  be  very  uni- 
formly regular  throughout,  and  exempt  from  flaws  or  strise. 

Before  commencing  operations,  the  wick  must  be  evenly 
trimmed  and  parted  in  the  middle,  so  that  when  the  jet  is 
placed  opposite  in  the  rear,  and  in  proper  relation,  it  may 
drive  the  flame  forcibly  in  advance,  but  not  of  too  great 
length,  else  it  will  become  smoky. 

The  tubes  or  rods,  previously  divided*  into  the  required 
length,  should  always  be  wiped  perfectly  dry  before  being 
subjected  to  the  action  of  the  flame,  and  then  carefully  and 
gradually  heated,  the  uniform  diffusion  of  the  heat  being 
effected  by  keeping  them  revolving ; — these  precautions,  which 
are  always  to  be  observed,  prevent  breaking  from  sudden  and 
unequal  heating.  After  being  heated,  they  must  be  removed 
gradually  from  the  fire,  and  laid  upon  a  piece  of  charcoal,  so 
as  to  become  annealed,  as  it  were,  by  gradual  cooling. 

The  most  simple  and  easily  performed  of  all  the  operations 

Fig.  403. 


of  glass-blowing,  is  the  rounding  of  edges,  which  is  readily 
done  by  heating  them  to  softness  in  the  flame  during  constant 

*  Tubes  can  very  readily  be  severed,  or  divided  into  lengths,  by  scratching 
them  with  a  file,  and  breaking  asunder  as  at  Fig,  407.  For  large  tubes,  the 
scratch  must  extend  entirely  around  the  circumference. 

Vessels  of  larger  diameters,  such  as  necks  of  retorts,  and  the  like,  require  the 
use  of  a  diamond  spark.  According  to  Mr.  Nasmyth,  coke  has  the  property  of 
cutting  glass,  and  can  very  well  be  substituted  for  the  diamond. 

When  the  scratch  of  the  file  is  insufficient  to  effect  a  smooth  division,  moisten 
the  scratch,  and  trace  it  with  a  heated  wire  or  pastile.  A  heated  wire  will 
also  divert  a  crack  in  a  glass  vessel  to  any  desired  direction. 


460  TUBES  CEMENTED. — TUBES  BENT. 

revolution  of  the  tube  between  the  thumb  and  three  fingers, 
which  support  it.  This  operation,  by  which  the  edges  of 
tubes  and  rods  are  smoothed,  is  also  preliminary  to  that  of 
widening  the  mouth  of  a  tube,  a  test-tube  for  example,  which 
is  done  by  spreading  it  while  hot,  as  shown  in  Fig.  403,  by 
means  of  the  iron  piercer,  or,  better,  the  biscuit  cone,  either 
of  them  being  previously  warmed,  and  then  carried  round  the 
opening  with  an  outward  pressure. 

Tubes  Gemented. — Tubes  or  rods  are  also  cemented  together 
by  softening  their  ends  and  blowing  gently  through  them  at 
the  moment  of  junction.     Care  must 
Fig.  404.  "be  taken   to  hold   them  firmly  and 

perfectly  even,  as  shown  in  Fig.  404, 
and  to  retain  hold  of  the  joined  tube 
until  it  has  entirely  cooled,  else  it 
may  bend  by  its  own  weight  at  the  heated  part,  and  thus  be- 
come crooked. 

If  the  tubes  to  be  cemented  are  of  unequal  diameters,  the 

wider  one  must  be  drawn  out  at 
Fig.  405.  its  end,  so  as  to  reduce  it  to  the 

size  of  the  smaller,  and  then  be 
joined  to  it  as  above  directed, 
and  shown  in  Fig.  405. 

Rods  are  cemented  together 
by  partially  fusing  their  ends  and  bringing  them  carefully 
together,  and  pressing  them  until  they  adhere.  The  welding 
is  then  completed  by  heating  the  new  joint,  during  which 
process,  in  order  to  impart  shape,  the  rods  must  be  kept 
rotating,  and  be  alternately  drawn  out  and  brought  together, 
until  the  junction  is  as  smooth  and  uniform  as  any  other  part 
of  the  surface. 

Tubes  Bent. — Very  small  tubes  can  be  bent  over  the  spirit 
lamp.  Fig.  115 ;  but  larger  ones  require  the  force  of  the 
blowpipe-flame  to  heat  them.  The  operation  of  bending  con- 
sists in  heating  the  tube,  to  dull  redness,  about  an  inch  on 
either  side  beyond  the  point  of  the  intended  curve,  and  just 
at  the  commencement  of  softening,  in  making  an  angle,  by 
bending  it  dexterously  but  slowly  in  the  desired  direction 
until  it  assumes  the  required  form.  In  order  to  prevent  a 
flat,  wrinkled,  and  consequently  very  fragile  elbow,  it  is  ne- 
cessary to  close  the  tube  at  one  end,  and  blow  gently  into  the 


DRAWING  OUT. — TUBES  CLOSED.  461 

otlier,  during  flexion,  so  that  the  pressure  of  the  air  within 
may  counteract  any  tendency  to  malformation. 

Drawing  Out. — When  a  tube  is  to  be  drawn  out,  either  as 
preliminary  to  further  working,  or  in  the  preparations  of 
nozzles  for  washing  bottles,  or  other  purposes,  one  of  the  pro- 
per size  is  taken,  at  the  ends,  between  the  thumb  and  index 
of  each  hand,  and  along  its  length  with  the  other  fingers, 
and  kept  revolving  gradually  over  the  flame  until  it  becomes 
red,  and  commences  to  soften  at  the  heated  part.  It  is  then 
taken  from  the  fire  and  drawn  apart,  as  shown  in  Fig.  406. 

Fig.  406. 


In  this  way  also  stirring  rods  are  pointed,  and  when  the  tips 
of  either  tubes  or  rods  thus  wrought  are  to  be  smoothed,  it  is 
only  necessary  to  divide,  or  break  across  the  centre  of  the 
part  drawn  out,  and  to  heat  the  surfaces  in  the  flame  until 
they  soften  and  fuse.  The  pro- 
per mode  of  severing  glass  rods  ^^s-  407. 
or  tubes,  is  first  to  make  a  deep 
scratch  with  a  three-cornered  file 
in  the  spot  where  separation  is 
required,  and  then,  after  grasping 
them  as  shown  in  Fig.  407,  by  gently  breaking  them  apart. 

The  tube  must  not  be  kept  in  the  fire  too  long,  nor  yet 
drawn  out  too  rapidly.  When  the  tube  or  rod  is  too  short  to 
be  divided,  it  may  be  drawn  out  at  either  of  its  ends  by  means 
of  a  punto — a  piece  of  glass  rod  which  is  heated  to  softness 
and  cemented  to  the  other  as  a  handle. 

Tubes  Closed. — Very  small  tubes  may  readily  be  closed 
by  softening  their  edges  over  a  flame,  and  rotating  them  until 
they  unite  and  adhere.  Tubes  of  larger  size  are  treated  in 
the  same  way,  but  to  facilitate  their  closure,  occasional  pres- 
sure of  the  hot  end  against  the  back  of  the  tool.  Fig.  402, 
and  sometimes  gentle  blowing  through  the  open  end,  are  re- 
quired. Tubes  also  are  closed  hermeti- 
cally by  drawing  out  one  end,  as  shown  Fig.  408. 
in  Fig.  408,  by  then  scratching  with  a 
file  and  breaking  asunder  the  part  a, 
and  finally  by  closing  the  small  orifice 
by  fusion  in  the  flame. 


462  DRAWING  OUT  AND  CLOSING. 

Drawing  Out  and  Closing, — When  it  is  desired  to  form  a 
vessel  like  a  test-tube,  a  tube  of  the  required  diameter  is 
drawn  out,  as  at  Fig.  409,  and  then  cut  asunder  at  a.     The 

Fig.  409. 


Fig.  410. 


two  pieces  thus  formed,  serve  to  make  two  test  tubes.  For 
that  purpose,  it  is  necessary  to  heat  the  smaller  end  of  each 
to  softness,  and  immediately  upon  removal  from  the  flame,  to 
blow  cautiously  and  slowly  into  the  open  extremity  until  the 
closed  end  assumes  a  uniform  spherical  shape.  Sometimes  it 
is  necessary  to  repeat  the  heating  and  blowing  in 
Fig.  411.  order  to  fashion  the  bottom  perfectly,  as  seen  in 
Fig.  411.  If  the  piece  of  glass  is  only  long 
enough  to  form  one  tube,  its  end  can  be  drawn  out 
by  attaching  a  punto,  as  before  described,  and  now 
shown  at  6,  Fig.  410.  This  punty,  or  glass  rod 
handle,  serves  also  to  remove  any  redundant  glass,  it  being 
only  necessary  for  that  purpose  to  heat  the  closed  end  highly, 
to  apply  the  punty  a  little  less  heated,  and  after  collecting 
upon  its  end  as  much  of  the  surplus  melted  glass  as  is  required 
to  make  the  bottom  thin  and  capable  of  supporting  sudden 
changes  of  temperature,  to  draw  it  off.  This  manipulation 
requires  some  dexterity,  which  is,  however,  easily  acquired  by 
slight  practice.  If  at  one  heating  and  gathering  the  bottom 
has  been  reduced  to  the  proper  thinness,  it  may  be  heated 
anew,  removed  from  the  fire,  and  then  by  slow  and  gentle 
blowing,  through  the  open  end,  the  bottom  may  be  blown  out 
to  roundness.  The  mouth  of  the  tube  is  then  finished  as  di- 
rected at  page  460,  Fig.  403. 

Lateral  Attachments. — To  attach  a  tube  to  the  side  of 
another  is  somewhat  difficult.  For  this  purpose,  the  tube 
with  which  the  junction  is  to  be  efiected  is  closed  at  one 
end  and  heated  at  the  desired  point,  such  as  5,  Fig.  412,  to 
high  redness.     To  this  hot  part  a  glass  rod,  or  punto  e, 


LATERAL  ATTACHMENTS  :  BULBS. 


463 


slightly  heated,  is  attached  and  drawn  out,  as  shown  in  the 
figure.     When  the  glass  has  cooled,  cut  off  the  new  joint  at 


Fig.  412. 


Fig.  413. 


u 


5,  heat  again  in  the  flame,  and  widen  its  mouth  with  the  tool, 
Fig.  400,  to  the  size  of  the  diameter  of  the  tube  which  is  to 
be  joined  with  it.  This  having  been  done,  the  tube  is  to  be 
attached  as  directed  at  page  460.  Fig.  413  shows  the  joint 
perfected. 

Another  mode  is  to  heat  and  close  the  drawn  out  end,  and 
to  blow  forcibly  through  the  tube  until  the  bulb,  thus  formed, 
bursts.  All  the  remains  of  the  thin  glass  bulb  being  broken 
off,  a  protruding  aperture  is  left,  to  which  the  lateral  tube 
may  be  cemented,  in  the  usual  way,  by  heating  the  edges  of 
the  ends  of  the  two  tubes  to  be  united,  joining  them  in  the 
flame  with  slight  compression,  heating  the  joint  to  redness, 
and  then  slightly  blowing,  to  give  form  and  prevent  cracking. 

To  Blow  Bulbs. — To  form  a  bulb  at  the  end  of  a  narrow  tube, 
it  is  only  necessary  to  continue  heating  it  after  closure  until  it 
commences  to  soften,  and  then  immediately  upon  its  removal 
from  the  flame,  to  blow  into  the  open 
end,  as  in  Fig.  414,  slowly,  until  the 
heated  part  expands  to  the  proper  size 
and  shape.  Care  must  be  taken  to 
heat  the  tube  to  a  sufficient  extent,  so 
that  there  may  be  enough  glass  soft- 
ened to  give  a  bulb  of  the  required 
size; — moreover,  during  both  the  heat- 
ing and  blowing  the  tube  must  be  kept 
slowly  rotating  between  the  fingers,  so 
as  to  prevent  an  accumulation  of  the 
melted  glass,  by  its  own  weight,  in 
any  one  part. 

To  blow  a  bulb  in  the  middle  of  a 
tube,  the  latter  must  be  heated  at  its  centre  during  constant 


Fig.  414. 


464  glass-blowing:  bulbs. 

but  slow  rotation  between  tbe  fingers,  and  then  carefully 
blown  into  at  one  end,  whilst  the  other  is  closed  with  the 
finger,  a  cork,  or  a  piece  of  wax.  The  pressure  of  the  air 
within  expands  the  hot  glass  into  a  spheroid,  regular  or  irre- 
gular in  form,  according  to  the  care  and  skill  of  the  operator. 
The  part  of  the  tube  to  be  expanded  must  be  heated  uniformly 
and  kept  in  constant  and  slow  revolution  during  both  the  heat- 
ing and  blowing. 

In  the  fashioning  of  certain  glass-tube  apparatus,  it  is 
sometimes  necessary  to  blow  the  bulbs  separately,  and  to 
attach  them  afterwards  to  their  adjacent  parts ; — the  bulb  is 
then  formed  as  follows.     Take  a  glass  tube  A,  Fig.  415,  of 

Fig.  415. 

»  n  A. 


the  required  diameter  and  length,  heat  it  at  the  points  a  and 
by  and  draw  it  out  in  two  places,  as  shown  at  t*  8  in  B.  When 
the  tube  has  cooled,  divide  it  at  the  attenuated  parts  r  s  with 
the  file,  as  directed  at  page  459,  Fig.  407,  and  close  one  end 
of  one  of  the  pieces  in  the  flame.  Then  hold  it  by  the  other 
end,  which  is  drawn  out,  heat  it  to  redness,  and  fashion  the 
bulb  by  blowing,  as  above  directed,  until  it  assumes  the  shape 
of  G.  It  is  then  cemented  to  the  other  parts  of  the  ap- 
paratus, as  directed  at  page  460,  the  previous  widening  of  the 
drawn  out  parts  being  performed  as  at  Fig.  403. 

Thermometer  bulbs  are  made  by  expanding,  as  above  di- 
rected, the  heated  end  of  tubes  with  a  capillary  bore. 

To  Make  a  Welter  8  Tube. — By  way  of  illustrating  the 
dififerent  operations  of  fashioning  glass  tubes  over  the  blow- 
pipe-flame, we  will  go  through  the  diflferent  stages  of  manu- 
facture of  the  safety  tubes  of  Welter.  A  straight  tube  is  first 
bent  into  form,  as  at  A,  Fig.  416,  and  the  flame  is  directed 
upon  a ;  as  soon  as  the  glass  softens  at  that  point  one  end  of 
the  tube  is  closed  with  the  finger,  and  the  other  is  blown  into 


GLASS-BLOWING  :   WELTER'S  AND  FUNNEL  TUBES.       465 


forcibly,  so  as  to  form  the  very  thin,  brittle  bulb  represented 

Fig.  416. 


l\ 


_»A 


X^ 

■1 

i! 

^ 

A. 


by  the  dotted  lines.  When  the  tube  is  thick  a  repetition  of  the 
heating  and  blowing  is  required.  This  bulb  is  then 
broken  off,  and  the  bent  tube,  thus  formed,  is  ready  to  ^ig-  ^^'^^ 
be  attached  to  the  straight  tube  B.  This  latter  is 
formed  of  a  separate  tube,  and  having  a  bulb  h 
blown  into  its  centre,  is  cemented  to  A  at  a,  in  the 
manner  before  directed.  The  funnel  top  of  the 
tube  B,  is  formed  by  first  blowing  a  bulb  c  on  its 
upper  end  to  extreme  thinness,  removing  it  with  the 
file  and  cementing  a  bulb,  with  open  mouth,  as  at 
a;  in  D.  The  S  form  is  given  merely  by  bending  B 
in  the  proper  direction. 

Instead  of  an  open  hulh  at  the  top  of  the  D  tube, 
a  small  funnel  is  cemented  to  it,  as  in  the  fashioning 
of  funnel  tubes,  Fig.  417. 


466  CORKS :  cork  borer. 


CHAPTER    XXXIII. 

CORKS. 

Corks  are  in  many  ways  indispensable  for  laboratory  pur- 
poses, and  the  stock  should  consist  of  all  sizes;  those  for 
mounting  apparatus  being  necessarily  of  the  finest  velvet  kind, 
smooth  and  as  free  as  possible  from  imperfections. 

An  excellent  means  of  increasing  the  elasticity  of  corks  is 
compression  by  a  small  apparatus.  Fig.  418,  sold  for  the  pur- 
Fig.  418. 


pose.     This  treatment  renders  them  capable  of  being  fitted  to 
apertures  with  great  nicety  and  ease. 

We  have  frequently  made  mention  of  the  adaptation  *'of 
tubes  and  other  parts  of  apparatus  by  means  of  perforated 
corks.  These  perforations  may  be  made  with  a  hot  metallic 
rod  and  afterwards  enlarged  with  a  rat-tail  file ;  but  a  much 
smoother  and  neater  hole  can  be  made  with  a  cork  borer,  Fig. 

Fig.  419. 


419,  which  is  intended  specially  for  this  purpose.     It  consists 


CORKS  PERFORATED. 


467 


Fig.  420. 


of  a  series  of  brass  tubes  of  uniform  length,  but  varying 
from  an  eighth  to  one  inch  in  diame- 
ter, and  fitting  one  within  the  other. 
The  sizes  contained  in  such  a  series 
are  equal  to  all  the  requirements  of 
the  laboratory,  as  holes  of  smaller 
or  larger  dimensions  than  the  above 
extremes  are  seldom  required.  Each 
of  the  tubes  is  open  below,  but  closed 
at  the  top  with  a  cap  c?.  Fig.  420, 
through  which  is  a  hole  h  for  the 
passage  of  a  stiff  wire  c?,  which  serves 
both  as  a  handle  and  as  a  punch  for 
ejecting  the  cores  from  the  tube 
after  the  perforation  of  the  cork. 

The  drawing  exhibits  one  of  the 
tubes  of  the  series  already  in  opera- 
tion, it  being  only  necessary  to  bring 
its  base  upon  a  cork,  and  to  effect 
the  perforation  by  pressure  upon  the  cap  and  a  slight  circular 
motion.  The  core  or  part  of  the  cork  removed,  ascends  into 
the  barrel  a  of  the  tube  and  must  be  ejected  by  the  force  of 
the  punch  d.  As  the  tubes  become  dull  on  the  edges,  they 
may  be  sharpened  upon  a  grindstone  or  with  a  fine  file. 

As  a  familiar  illustration,  we  exhibit  in  the  Fig.  421  a  cork 

Fig.  421. 


thus  treated  with  tubes  inserted  in  the  perforations.  Their 
convenience  is  shown  in  many  of  the  arrangements  of  which 
we  have  given  drawings. 

When  the  corks  are  not  of  good  quality,  they  may  be  ren- 
dered impermeable  by  coating  their  surfaces  with  8oft  cement, 

India  rubber  corks  have  lately  appeared  in  the  market ; — 
they  are  made  by  Goodyear,  and  answer  admirably  as  cheap 
stoppers  of  bottles  containing  substances  which  are  volatile, 
and  which  do  not  corrode  the  caoutchouc. 


468      DEALERS  IN  AND  MANUFACTURERS  OP  APPARATUS. 


CHAPTER   XXXIV. 

DEALERS  IN  AND  MANUFACTURERS  OF  APPARATUS. 

For  the  convenience  of  those  engaged  in  the  study,  prac- 
tice, or  teaching  of  chemistry,  we  here  introduce  the  address 
of  a  number  of  prominent  dealers  in  and  manufacturers  of  the 
required  furniture  and  reagents.  From  one  or  more  of  them 
may  be  obtained  each  and  every  implement  and  article  men- 
tioned in  this  work.  Some  few  issue  catalogues  of  their 
articles,  with  the  price  of  each  affixed,  and  furnish  them 
gratuitously  upon  application ; — their  names  are  designated 
in  the  list  below  by  asterisks. 

Joaquim  Bishop,  Laurel  Street,  Philadelphia;  manufacturer 
of  platinum  vessels,  and  of  all  kinds  of  chemical  or  philoso- 
phical metallic  apparatus. 

Bently  &  Co.,  Baltimore;  manufacturers  of  portable  steam 
generators ;  Morris,  Tasker  &  Co.,  Agents,  Philadelphia. 

Charles  Button*,  146  Holborn  Bars,  London;  dealer  in 
chemical  apparatus,  and  manufacturer  of  pure  chemicals. 

J.  P.  Duffey,  South  Eighth  Street,  Philadelphia ;  manufac- 
turer of  delicate  balances,  and  of  chemical  and  philosophical 
apparatus  generally. 

Wm.  Debeuist,  University  of  Pennsylvania,  Philadelphia; 
manufacturer  of  metallic  apparatus. 

Joseph  Fisher,  58  Chestnut  Street,  Philadelphia ;  manufac- 
turer of  thermometers  and  hydrometers. 

L.  C.  Francis,  No.  13  Dock  Street,  Philadelphia;  manu- 
facturer of  thermometers,  barometers,  and  of  metallic  appa- 
ratus. 

James  Green,  Baltimore ;  manufacturer  of  electrical  and 
other  metallic  apparatus. 

Richard  Griffin  &  Co.*,  Glasgow,  Scotland;  dealers  in  che- 
mical apparatus  and  reagents. 

J.  G.  Greiner*,  Berlin,  Prussia,  manufacturer  of  accurate 
thermometers  and  hydrometers  for  experimental  research. 


DEALERS  IN  AND  MANUFACTURERS  OF  APPARATUS.      469 

B.  B.  Gumpert,  120  North  Second  Street ;  manufacturer 
of  electro-magnetic  machines. 

Hammet  and  Hiles,  128  Vine  Street,  Philadelphia ;  manu- 
facturers of  copper  hollow  ware. 

Haig  &  Co.,  545  North  Second  Street,  Philadelphia;  manu- 
facturers of  blue  stoneware. 

Stephen  Heintz,  Queen  above  Warren,  Kensington,  Phila- 
delphia }  glass  blower  and  manufacturer  of  all  kinds  of  tube 
apparatus. 

Kartell  and  Lancaster,  Union  Glass  Works,  Kensington, 
Philadelphia;  manufacturers  of  tube  apparatus,  and  of  all 
other  kinds  of  chemical  glassware. 

Hansell,  Pine,  above  Tenth  Street,  Philadelphia ;  turner  in 
wood,  and  manufacturer  of  supports,  clamps,  and  filter  stands. 

Edward  N.  Kent*,  116  John  Street,  New  York ;  general 
depot  for  the  sale  of  all  kinds  of  chemical  and  philosophical 
apparatus,  and  of  pure  chemicals. 

Lindsay  &  Blakiston*,  North-west  corner  of  Fourth  and 
Chestnut  Streets,  Philadelphia ;  publishers  and  importers  of 
scientific  books. 

Abraham  Miller,  Zane  Street,  Philadelphia ;  manufacturer 
of  assay  furnaces  and  of  all  kinds  of  pottery. 

Alva  Mason,  South  Fifth  Street,  Philadelphia;  manufac- 
turer of  chemical  and  philosophical  apparatus. 

Powers  &  Weightman,  corner  of  Ninth  and  Parrish  Streets, 
Philadelphia;  manufacturers  of  acids  and  pure  chemicals,  and 
of  chemical  glassware. 

Z.  Pike,  New  York;  manufacturer  of  chemical  and  electrical 
apparatus. 

Mauldin  Perrine,  Baltimore ;  manufacturer  of  blue  stone- 
ware retorts,  adapters,  crystallizers,  digesters  and  other  ap- 
paratus, of  the  same  material,  for  chemical  uses. 

Bullock  &  Crenshaw*,  North-east  corner  of  Sixth  and  Arch 
Streets,  Philadelphia;  manufacturers  of  and  dealers  in  pure 
chemicals,  glass  and  porcelain  apparatus. 

Savery  &  Co.,  corner  of  Reed  and  Front  Streets,  Philadel- 
phia ;  manufacturers  of  plain  and  enamelled  hollow-ware  of 
iron. 

Tatham  &  Brothers,  Philadelphia ;  manufacturers  of  smooth 
lead-pipe. 

L.  Voigt,  North  Third,  above  Vine  Street,  Philadelphia ; 
Agents  for  Storms  and  Fox's  glassware. 


f 


470      DEALERS  IN  AND  MANUFACTURERS  OF  APPARATUS. 

Jas.  M.  Wightman*,  33  Cornliill,  corner  of  Franklin 
Avenue,  Boston ;  manufacturer  of  metallic  chemical  and  phi- 
losophical apparatus. 

E.  Wight,  No.  4  South  Fifth  Street,  Philadelphia;  manu- 
facturer of  philosophical  apparatus. 

Weiss  &  Schively,  43  North  Front  Street,  Philadelphia; 
importers  of  Beindorff's  portable  laboratories;  of  glass  and 
porcelain  ware,  and  of  fine  drugs  and  chemicals. 

Samuel  Wenzell,  corner  of  Queen  and  Palmer  Streets, 
Kensington,  Philadelphia ;  manufacturer  of  laboratory  tables, 
mineral  cases,  and  wooden  apparatus. 


INDEX 


ABsonpTioN  of  gases,  257 
Acids,  filtration  of,  361 
Aikin's  blast  furnace,  155 
Air  chambers,  324 

desiccation  in,  324 
pump,  59 

eudiometrical  analysis  of,  426 
Alcohol  bottle  for  table  use,  72 
Alterable  substances,  desiccation  of,  336 
Amalgam  for  electrical  machines,  412 
Amalgamation  of  copper  wires,  440 

zinc  plates,  434 
Ampere's  formula  for  the  direction  of 

currents,  452 
Analysis,  record  of,  53,  73 
of  gases,  426 
by  mouth  blowpipe,  380 
Analytic  balance,  95 
Analyzer,  392 

Anode  of  a  voltaic  circuit,  432 
Anvil,  the,  50,  382 

Apparatus,  advice  in  the  purchase  of, 
74 
Ventzke's,  395 
Beindorfi^'s,  187 
dealers  in  and  manufactur- 
ers of,  468 
Aqueous  fusion,  192 
Areometer,  116,  120 

Nicholson's,  119 
Argand  burner  for  gas,  59 
Assaying,  220 
Assay  furnace,  155 
Astatic  galvanometer,  451 


Bags,  gas,  216 


Balance  room,  34 

table,  34 

platform,  61 

laboratory,  84 

requisite  conditions 
of,  86 

the  mint,  88 

excellence  of,  92 

Kater's,  92 

Robinson's,  92 

Berlin,  95 

Tralle's,  96 

preservation  of,  98 

hydrostatic,  112 

of  torsion,  424 
Basins,  supports  for,  158 
Baths,  179 

construction  of,  180 
heating  by,  180 
advantages  of,  180 
evaporation  over,  326 
desiccation  by  means  of,  335 
heated  by  gas,  39,  56 
sand,  37,  39,  56,  151,  186 
steam,  42,  181 
water,  182,  183 
saline,  184 
metallic,  185 
oil,  185 
mercury,  185 
filter,  358 
Battery,  electrical,  417 

WoUaston's,  432 

Daniell's,  435 

constant,  434 

Smee's,  436 

Grove's,  437 

Bunsen's,  438 

Bird's,  439 

made  of  blue  pots,  439 

mode  of  connecting,  439 


472 


INDEX. 


Bee-hive  shelf,  268 
BeindorfF's  apparatus,  187 
Bell  glasses,  266 

graduated,  109,  266 
capped,  266 
Bench,  work,  50 
Bennet's  electrometer,  421 
Bird's  battery,  439 
Binding  screws  for  connecting  batteries, 

439 
Berzelius's  lamp,  54 
Black  varnish,  58 
board,  63 

lead  crucibles,  194 
flux,  207 
Black's  blowpipe,  372 
Bladders,  cleansed,  271 

filled  with  gas,  271 
Blast  furnace,  54,  1 54 

Sefstrom's,  155 
Aikin's,  155 
Blowing,  glass,  456 

Blowpipe  table,  blast,  54,  58,  155,  168 
mouth,  58,  388 
manipulation,  367 
use  and  construction  of,  368 
Gahn's,  370 
Wollaston's,  369 
Mitscherlich's,  371 
Black's,  372 
economical,  372 
lamp  and  appliances,  373 
flame  and  blast,  374,  376 
mode  of  holding,  376 
detection    of    volatile    sub- 
stances by  means  of,  379 
instruments  for  analysis  by, 

380 
test  series,  390 
compound,  171,  263 

fusion  by,  201 
Blue  pots,  194 
Boiling,  149,  307 

by  steam,  41,  43,  312,  321 
in  tubes,  307 

beaker  glasses,  310 
flasks,  310 
capsules,  311 
vats,  Duvoir's,  321 
points   of  saturated  solutions, 
184 
Books,  preservation  of,  32,  33 

for  recording  analyses,  53 
laboratory,  73 
Borer,  charcoal,  381 


Bottles,  cleansing  of,  49 

glass,  Bohemian,  64 
green,  64 

labelled,  66 

removal  of  corks  from,  68 

test,  68 

for  table  use,  72 

specific  gravity,  115,  117 

Wolffe's,  258 

spritz,  356 

washing,  357 
Buckets,  51 

Burner,  Argand  gas,  59 
Bulb  rests,  178 
Bulbs,  glass,  blown.  463 
Bunsen's  battery,  438 


Cadet's  mode  of  solution,  319 
Calcination,  149,  210 
Calcining  furnace,  ir3 
Calorimotor,  Hare's,  447 
Cambridge  lamp,  166 
Camphor,  pulverization  of,  84 
Capsules,  311 

Carbonic  oxide,  reduction  by,  218 
Case,  test,  68 
Cements,  276 

for  labels,  279 
Centigrade  thermometer,  139 
Centre  table,  56 
Chamber,  drying,  35 
Charcoal,  repository  of,  51 

as  fuel  for  furnaces,  154, 157 

reduction  by,  213 

borer,  381 

ignited  by  galvanism,  445 

prepared  for  galvanic  expe- 
riments, 446 
Chemicals,  requisite  stock  of,  72 
Chemical   reaction,  crystallization   by, 

332 
Chemist,  working  costume  of  the,  72 
Chest,  tool,  50 
Chimney  lamp,  54 
Chlorcalcium  tube,  341 
Circuit,  simple  galvanic,  431 
Circular  polarization,  393 
Clay  crucibles,  193 
Cleansing  apparatus,  50 

of  glass,  48 
CleanUness  enjoined,  72 


INDEX. 


473 


Clerget's  method  of  analysis,  403 

Cloths,  filtering,  359 

Coal  cylinders  for  batteries,  439 

Cohobation,  250 

Coke,  51 

as  fuel  for  furnaces,  157 
for  cutting  glass,  459 
Coking,  211 

Collection  of  gases,  254 
Compound  blowpipe,  171,  263 
Condenser,  Liebigs, 239 
Connection  of  batteries,  439 
Construction  of  baths,  180 

formulae,  452 
Contents,  table  of,  vii 
Contusion,  75 
Cooler,  234 
Cooling  mixtures,  190 
Corks,  repository  for,  57 
borer,  57,  466 
removed  from  bottles,  69 
softened,  466 

rendered  impermeable,  466 
perforated,  467 
India  rubber,  467 
Costume,  laboratory,  72 
Coulomb's  electrometer,  424 
Crown  of  cups,  431 
Crucibles,  50 

manufacture  of,  197 

supports  for,  158 

jacket,  164 

position  in  furnace,  154 

heated  over  blowpipe  flame, 

170 
directions  for  heating,  54, 1 98 
clay,  193 
Hessian,  1 93 
London,  193 
French,  193 
black  lead,  194 
porcelain,  194 
metallic,  195 
iron,  195 
silver,  196 

platinum,  53,  196,  197 
sublimation  in,  228 
Crystallization,  149,  328 

by  fusion,  328 
by  sublimation,  328 
from  solution,  329 
by  chemical    reaction, 
332 
Crystals,  purification  of,  331 
Cupboards,  62 

31 


Cupel  furnace,  156 

Cupellation,  149,  222 

Cupels,  220 

Curtains,  rendered  fire  proof,  29,  62 

Cushion,  for  electrical  machine,  411 

Cylinder  electrical  machine,  409,  411 

Cyhnders,  fire,  44 


Daniel's  pyrometer,  137 

constant  battery,  434 
Darcet's  digester,  305 
Dealers  in  and  manufacturers  of  che- 
micals and  apparatus,  468 
Decantation,  345 

washing  by,  364 
Decoction,  149,  300 
Decolorization,  397 
Decrepitation,  212 
Deflagration,  149,213 
Density   of  bodies,   determination   of, 

112 
Desiccation,  149,  333 

by  means  of  baths,  335 
in  air  chambers,  334 

vacuo,  338 
of  gases,  340 
liquids,  339 
solids,  333 

easily      alterable     sub- 
stances, 7,  336 
Desk,  drawing,  3 1 

writing,  30 
Deville's  gasometer,  265 
Diaphragms  for  galvanic  batteries,  435 
Difi"erential  thermometer,  142 
Digester,  D'Arcet's,  305 

Mohr,  306 
Digestion,  54,  149,  153,  301 

in  beaker  glasses,  302 

flasks,  303 
under  pressure,  304 
Discharger,  electrical,  419 
Displacement,  313 

solution  by,  314 
Distillation,  44,  149,  225 

destructive,  232 
dry,  274,  232 
gaseous,  250 
in  tubes,  240 

retorts,  235,  238 
in  vacuo,  273 
liquid,  232,  245,  249 


474 


INDEX. 


Distillation,  solid,  232 

the  cooler,  234 
micro-chemical,  240 
rules  for,  243,  244 

Division,  84  to  75 

by  slicing,  75 
contusion,  76 
chemical  means,  83 
elutriation,  82 
granulation,  83 
levigation,  82 
porphyrization,  79 
rasping,  75 
trituration,  79 
intermedia,  83 

Donovan's  filter,  362 

Draining  racks,  48 

Dropping  tubes,^106 

Drummond  light,  174 

Drying  chamber,  35 
tubes,  340 

Duvoir's  boiling  vats,  321 

Dye-woods,  exhaustion  of,  43 


Earthen virare  retorts,  243 
Ebullition,  307  , , 

Economical  blowpipes,  372 
Edulcoration,  365,  384 
Efflorescence,  333 
Electrical  spark  in  eudiometry,  428 
machine,  cylinder,  409 

plate,  413 
battery,  47 
Electricity,  409 

detection  and  measurement 
of,  421 
Electro-chemical  decomposition,  441 

magnetic  multiplier,  450 
Electrolysis,  441 
Electrolytes,  441 

Electrometer,  Henley's  quadrant,  420 
Bennet's,  421 
opposite    electricities  in- 
dicated by,  424 
induction  of  electricity  in, 

423 
condensing,  424 
Coulombs,  424 
Electrophorus,  420 
Electroscope,  382 
Electrotype,  436 
Elutriation,  82 


Etching  upon  glass,  66 

Eudiometer  tubes,  graduation  of,  132 

Hare's,  446 
Eudiometry,  426 
Evaporating  furnace,  153 

vessels,  323 
Evaporation,  149,  153,  322 

spontaneous,  323 

in  vacuo,  324 

by  heat  in  open  air,  325 

over  baths,  326 

by  steam,  326 
heated  air,  326 

over  naked  fire,  327 


Fahrenheit's  thermometer,  13j9 
Faraday's  voltameter,  443 

■     tube  for  collection  of  gases 
.     in  efectrolysis,  443 
Filter  baths,  ^58 

■*       papers,  Kent's,  52 
'^        stands,  177 
Filtering  apparatus,  354 

directions  for,  355 
paper,  52,  349 

'   German,  349 
Swedf^h,  349 
repository  for,  57 
•  clotbs,  58 
Filters,  folded, 353 

introduced  into  funnels,  353 
plain,  352 
plaited,  352 
ignition  of,  201,  55 
desiccation  of,  35 
washing  of,  374 
Donovan's,  363 
Riouffe's,  363 
Jennison's,  47 
Filtration,  345,  348 

promoted  by  warmth,  358 
hot,  arrangement  for,  35 
through  paper,  348     ^ 
cloths,  359 
pulverulent   matter, 
361 
of  acids,  361 

corrosive  liquids,  361 
volatile  liquids,  363  * 

Fire  cylinder,  44 

lute,  vessels  coated  with,  278 
Flame,  blowpipe,  374 


INDEX. 


475 


Flasks,  310 

Florence,  253 
specific  gravity,  115,  117 
supports  for,  158 
sublimation  in,  227 
solution  in,  310 
Flexible  tubes,  216 
Florence  flasks,  253 
Florentine  receivers,  249 
Flowers,  distillation  of,  45 

by  sublimation,  228 
Fluids,  specific  gravity  of,  determined, 
117 
by  flasks,  118 
hydrometers,  119 
measuring  of,  128 
Flux,  black,  and  its  equivalent,  217 
Fluxes,  metallic,  209 

non-metallic,  206,  204 
ignition  with,  203 
Fluxing,  149,  203 
Formulae,  construction  of,  452 
Freezing  mixtures,  189,  191 
French  crucibles,  193 
Fuel,  168 

Funnel  tubes,  manufacture  of,  465 
Furmels,  filtering,  350 

separatory,  350 
ribbed,  350 

glass,  350  ^X 

porcelain,  351      -  ^<^      ''• 
stone,  351  "    "^ 

supports  for,  354 
filters,  placed  in,  353 
Furnaces,  room,  its  arrangement,  34 

laboratory,    its  construction, 

35,38 
Luhme's  (portable),  39,  150 
Kent's  (portable),  39,  152 
Still,  44 
'blast,  54, 154 
tongs,  159 
stationary,  149 
universal,  150,  152 
table,  150 
evaporating,  153 
calcining,  153 
reverberatory,  153 
assay,  155 
Sefstrom's  blast,  155 
Aikin's  blast,  155 
cupel,  156 
Liebig's,  157 
furniture,  158 


Furnaces,  management  of,  157 
Fusion,  149,  171,  192 
igneous,  192 
aqueous,  192 

of  bodies  inalterable  by  air  or 
heat,  199 

alterable  by  heat,  200 
alterable  in  air,  200 
of  diflficultly  fusible  substances, 

201 
by  hydrogen  blowpipe,  201 
crystallization  by,  328 


Gahn's  blowpipe,  370 
Gallows'  screw,  54 
Galvanic  currents,  direction  of,  452 
light  and  heat,  445 
battery,  Wollaston's,  432 
Daniell's,  434 
Smee's,  436 
Grove's,  437 
Bunsen's,  438 
Galvanism,  431 

precipitation  by,  344 
applied  to  eudiometry,  446 
decomposition  of 
fluids,  443 
'  heat  and  light  produced  by, 
444 
Galvanometer,  449 

astatic,  451 
Gas,  generation  and  absorption  of,  172, 
173,  257 
illuminating,  168 

from  grease,  169 
mode    of    burning, 

55 
heatmg  by,  39, 54 
lamp,  54,  168 

for  laboratory  operations,  55 
bags,  216 
jars,  266 
receivers,  266 

reservoir,  self-regulating,  173 
collected  over  water,  268 
air,  270 
mercury,  270 
transfer  into  bell-glasses,  271 
bladders,  271 
from  gasometers,  263 


476 


INDEX. 


Gaseous  distillation,  232 
Gases,  correction  of,  for  pressure,  1 1 0, 
272 

temperature, 
110,  292 
solubility  of  tested,  282 
solution,  286 
liquefaction,  286 
solidification,  286 
conducted  into  gasometers,  262 
weighing  of,  108 
measurement  of,  133 
specific  gravity  of,  determined, 

122 
distillation  of,  250 

tube     apparatus 
for,  252 
collection  of,  254 
desiccation  of,  340 
(Gasometers,  261 

filled,  262 

gases,    transferred    from, 

263 
Pepy's,  261 
mercurial,  263 
Deville's,  265 
Generator,  steam,  39 
Glass,  etching  upon,  66 
tubes,  219 
retorts,  236 
funnels,  350 

vessels,  exhausted  of  air,  109 
Glass-blowing,  455 

tables  for,  457 
lamp  for,  457 
implements  for,  458 
position    and    manage- 
ment of  the  tube  over 
the  flame,  459 
cutting,  459,  461 
tubes  cemented,  460 
bent,  460 
drawn  out,  461 
closed,  462 

bulbs  blown,  463,  464 
tubes,   edges    of,   widened   and 
smoothed,  459 
Glasses,  cleansing  of,  49,  66 
repository  for,  62 
Bell,  266 
Gold,  pulverization  of,  84 
Graduates,  129 

Graduation  of  vessels,  128,  131 
Granulation,  83,  330 


Gravimeter,  Nicholson's,  119,  122 
Grove's  battery,  437 


H 


Hare's  compound  blowpipe,  171 
sliding  rod  eudiometer,  446 
calorimotor,  447 
Heat,  sources  and  management  of,  149 
and  light  produced  by  galvanism, 
444 
Heating  by  baths,  180 
Henley's  quadrant  electrometer,  420 
Henry's   apparatus   for  hydrosublima- 

tion,  230 
Hessian  crucibles,  193 
Hoods  for  furnaces,  26,  39 

retorts,  244 
Horsford's  lamp,  166 
Hydrogen,  generation  of,  173 
reduction  by,  213 
Hydrometers,  58,  119,  120 

mode  of  using,  121 
Hydrometric  degrees,  table  of,  121 


I&  J 

-Jacket,  crucible,  164 
Jars,  gas,  266 

Ley  den,  416 
Jennison's  filter,  47 
Igneous  fusion,  1 92 
Ignition,  54,  149,  201 
of  filters,  201 
of  bodies  in  vapors,  202 
with  fluxes,  203 
for   determination   of   hygro- 
scopic matter,  202 
Incineration,  149,  211 
Indelible  labels,  66 
Index  rerum,  69 

India  rubber  apparatus,  repository  for, 
57 
tubes,  use  and  manufac- 
ture of,  215 
gas  bags,  216 
door  springs,  29 
Infusion,  300 
Ink  for  labels,  69 

Intensity  of  galvanic  fluid,  433,  435, 
444 


INDEX, 


m 


Iron  crucibles,  195 
retorts,  218 
tubes,  241 


Kater's  balance,  92 
Kathode  of  a  voltaic  circuit,  432 
Kennedy's  air-pump,  60 
Kent's  furnace,  39,  152 
Ker's  tube,  135 

Kettle  for  constant  supply  of  hot  water, 
66 


Labelling,  importance  and  necessity  of, 

65 
Labels,  65 

rendered  indelible,  65 
La  Rue  &  Co.'s,  66 
etched,  66 
ink  for,  69 
cement  for,  279 
Laboratory,  construction  of,  27,  28,  29 
arrangement  of,  25,  30 
lighting  of,  26 
ventilation  of,  26 
costume,  72 
book,  73 

operations,  record  of,  53 
portable  (Beindorff's),  186 
Lamp,  spirit,  54,  160 

Berzelius's,  54,  153 
gas,  54,  168 
glass,  160 
Rose's,  166 
Russian,  167 
Horsford's,  166 
Cambridge,  166 
Luhme's,  165 

blowpipe  and  appliances,  373 
glass-blower's,  457 
oil,  162 

tongs,  161,  170 
supports,  164 
Lamps,  heating  over,  160 

tubes  heated  by,  162 
Levigation,  82 
Leyden  jar,  416 

residual  charge  of  the,  419 
Liebig's  furnace,  157 

bulbed  receiver,  256 

31* 


Light,  26 

sky,  disadvantages  of,  26 
Drummond,  174 
analysis  by  polarization  of,  391 
Liquefaction  of  gases,  286 
Liquid  distillation,  232 
Liquids,  slow  evaporation  of,  35 
weighing  of,  106 
transfer  of,  in  dropping  tubes, 

106 
distillation  of,  245,  247 

volatile,  249 
solution  of,  286 
filtration  of  corrosive,  361 

volatile,  361 
desiccation  of,  339 
Local  action  upon  the  zinc  of  batteries, 

433 
London  crucibles,  193 
Low  temperatures,  mode  of  producing, 

188 
Luhme's  furnace  ("mwiWsoZ"),  39, 150 

lamp,  165 
Lute,  vessels  coated  with  fire,  278 
Lutes,  274 

application  of,  279 


M 


Maceration,  299 
Magnet,  383 
Maneigement  of  heat,  149 

furnaces,  157 
Manipulation,  blowpipe,  367 
Marsh's  tube  apparatus,  253 
Mastich,  Hamelin's,  27 
Measurement  of  temperature,  136 
Measures,  129 

of  capacity,  value  in  inches, 
133 
Measuring  of  fluids,  128 
gases,  133 
Melloni's  thermomultiplicator,  142 
Mercury  bath,  185 
trough,  269 
gasometer,  263 
cups  for  connecting  batteries, 
440 
Metals,  division  of,  77,  83 

fusing  point  of,  138 
Metallic  crucibles,  195 
tubes,  218 
batlis,  185 


478 


INDEX. 


Micro-chemical  distillation,  240 
Microscope,  381 
Minerals,  preservation  of,  30 
cases,  31 

for  analysis,  78,  82 
Mitscherlich's  blowpipe,  371 
Mixtures,  freezing,  189 
Mohr's  digester,  306 
Mortar  iron,  51,  76 

steel,  78 

agate,  79,  382 

porcelain,  79 

wedgewood,  79 

glass,  80 
Mother  waters,  treatment  of,  330 
Muffles,  222 

Taylor's,  223 


N 


Neutralization,  280 
Nicholson's  gravimeter,  117 
Nobili's  astatic  galvanometer,  451 


Office,  arrangement  of,  30 
Oil  bath,  185 

lamp,  162 

olive,  162 
Operating  room,  the,  51 
table,  the,  52 
Ores,  pulverization  of,  77 
Oxygen,  apparatus   for  generation  of, 

172 
Oxy-hydrogen  blowpipe,  174 


Paper  filters,  349 

filtering,  German,  349 
Swedish,  349 
repository  for,  57 

Pepy's  gasometer,  261 

Phosphorus,  pulverization  of,  83 

Pincettes,  380 

Pipettes,  107 

Plain  filters,  352 

Plaited  filters,  352 

Plate  electrical  machine,  413 

Platinum  crucibles,  196,  197 
tubes,  219 


Platinum  retorts,  241 

foil  in  batteries,  439 

used  for  electrodes,  441,442, 

444 
wires  ignited  by  galvanbm, 
446 
Pliers,  381 

Plumbago  crucibles,  battery  of,  439 
Pneumatic  pump,  60 

syringe,  60,  267 
troughs,  265 
Polarization  of  light,  analysis  by,  391 
Polarizer,  392 

Poles  of  a  simple  galvanic  circuit,  431 
a  compound  galvanic  circuit, 

432 
platinum  for  electrolysis,  441, 
442 
Porcelain  retorts,  242 
tubes,  218 
crucibles,  194 
funnels,  351 
Porphyrization,  79 
Portable  laboratory,  186 
Pots,  blue,  194 
Pouring,  346,  356 
Precipitates,  desiccation  of,  35 

washing  of,  364 
Precipitation,  342 

directions  for,  343 
by  galvanism,  344 
vessels  for,  343 
Press,  320 

Pressure,  digestion  under,  304 
Prisms,  Nicholson's,  392 
Pulverization,  77 

Purchase  of  apparatus,  advice  as  to,  74 
Purification  of  crystals,  331 
Pyrometer,  136 

Daniell's,  136 
Pyroxylic  spirit,  160,  168 


Q 


Quantity  of  the  galvanic  fluid,  433, 441 , 
444 


R 


Rack,  test,  the,  179 

tube,  62  ' 
Reaction,  chemical,  crystallization  by, 
332 


INDEX. 


479 


Reagents,  the  series  of,  69 

purity  of,  72 
Reaumur's  thermometer,  139 
Receivers,  238,  239,  246 

bulbed,  Liebig's,  256 
gas,  266 
Florentine,  249 
Record  of  analyses,  73 
Rectification,  250 
Reduction,  149 

by  chemical  means,  83 
charcoal,  213 
hydrogen,  215 
carbonic  oxide,  218 
apparatus,  215 
tubes,  179,  218 
Refrigerant,  the,  44 
Rerum,  index,  73 
Reservoir,  self-regulating,  173 
Rests,  tube  and  bulb,  178 
Retorts,  glass,  53,  236 
porcelain,  242 
earthenware,  243 
stoneware,  243 
iron,  241,  254 
platinum,  241 
mode  of  filling,  247 
adapted  to  tubes  and  receivers, 

247 
sublimation  in,  228 
distillation  in,  235,  238 
selection  of,  236 
repository  of,  62 
supports  for,  176,  177 
Reverberatory  furnace,  153 
Rioufie's  filter,  363 
Roasting,  149,  211 

in  tubes,  218 
Robinson's  balance,  92 
Room  balance,  arrangement  of,  34 
furnace,  arrangement  of,  34 
operating,  arrangement  of,  5 1 
Roots,  distillation  of,  45 
Rose's  lamp,  166 
Rubber  of  electrical  machine,  411 

amalgam 
for,  4 12 
Russian  lamp,  167 


S 


Saccharimeter,  Soleil's,  399 
Saccharine  substances,  analysis  of,  391 
Safety  tubes,  259 


Saline  baths,  184 

Salts,  table  of  the  solubility  of,  287 
Sand,  39,  57,  153,  185 
baths,  38,  39 
•  table,  56 
temporary,  186 
Saturated  solutions,  boiling  points  of, 
-184 

Saturation,  280,  285 
Schweigger's  galvanometer,  450 
Screw,  gallows',  54 
Sefstrom's  blast  furnace,  155 
Separatory  funnels,  350 
Series,  the  test,  69 
Sieves,  80 
Sifting,  81 

Silica,  pulverization  of,  84 
Silicious  stones,  pulverization  of,  77 
Silver,  pulverization  of,  84 
crucibles,  196 

platinized,  for  Smee's  battery, 
436 
Sink,  the,  46 

Skylight,  disadvantages  of,  26 
Slicing,  75 
Smee's  battery,  436 
Soleil's  saccharimeter,  398 
Solid  distillation,  232 
Solidification  of  gases,  286 
Solids,  weighing  of,  104 

specific   gravity,  determination 

of,  112 
solution  of,  283 

influenced   by  tem- 
perature, 284 
modes  of  effecting,  285 
desiccation  of,  333 
Solubility,  mode  of  testing,  281 

of  salts,  table,  287 
Solution,  149 

simple,  280 

chemico-mechanical,  280 
saturated,  280 
of  solids,  283 
liquids,  286 
gases,  286 
by  boiling,  286 
steam,  286 
displacement,  313 
in  close  vessels,  317 
under  pressure  of  steam,  32  . 
Cadet's  mode  of,  319 
means  of  facilitating,  282 
crystallization  from,  329 
Solutions,  decolorization  of,  397 


480 


INDEX. 


Solutions,  saturated,  boiling   points  of, 

184 
Sources  of  heat,  149 
Spatulas,  53 

Specific  gravity,  determination  of,  112 
of  solids,  112 
fluids,  117 
gases,  122 
vapors,  126 
by  means  of  the  bal- 
ance, 112 
by  means  of  the  flask, 

115,  117 
by  means  of  the  hy- 
drometers, 119 
by  means  of  the  gra- 

vimeter,  116 
bottles,  115 
Spirit  lamp,  54, 161 
pyroxylic,  168 
Spontaneous  evaporation,  323 
Spritz  bottles,  356,  365,  384 
Stands,  filter,  177 
Steam  generator,  the,  39,  41 
baths,  42,  181 
solution  by,  312 
boiling  by,  321 
evaporation  by,  326 
Stench  trap,  47 
Still,  43,  233 

furnace  for,  44 
Stock  for  laboratory,  72 
Stoneware  retorts,  243 
Strainers,  359 

Straining  through  cloths,  360 
Sublimation,  149 

crystallization  by,  328 
implements  of,  225 
in  tubes,  226 
flasks,  227 
retorts,  228 
crucibles,  228 
shallow  vessels,  229 
Ure's  apparatus,  230 
Henry's  apparatus,  230 
Substances,  division  of,  75 
Sugar,  analysis  of,  bv  polarization  of 

light,  391 
Sulphate  of  copper  used  in  batteries, 

435 
Sulphur,  pulverization  of,  84 
Supports  for  tall  vessels,  106 
funnels,  354 
crucibles,  158 
flasks  and  basins,  158 


Supports,  lamp,  164 

Gray  Lussac's,  176 

Gahn's,  177 

universal,  176 

blowpipe  operations,  377 
Sjrphon  eudiometer,  429 
Syphons,  349 
Syringe,  108 

pneumatic  ,267,  358 
Syrups,  filtration  of,  362 


Table,  balance,  34 
operating,  52 
blowpipe,  blast,  54,  58, 169,  458 

mouth,  58,  388 
centre,  56,  57 
furnace,  150 

of  hydrometric  degrees,  121 
thermometrical  equivalents, 

144,  149 
value  of  measures  of  capacity 
in  cubic  inches,  133 
for  the  analysis  of  saccharine 

substances,  405 
for  glass-blowers,  456 
of  boiling  points  of  saturated 
solutions,  184 
solubility  of  salts,  287,  299 
Temperature,  measurement  of,  136 

low,  mode  of  producing, 

188 
influence  of,  in  efiecting 
solution,  285 
Test  series,  69 

rack,  53,  179 
case,  68 
bottles,  68 
tubes,  308 
Thermometers,  58,  136 

Fahrenheit's,  139 
Centigrade,  139 
Celsius's,  139 
Reaumur's,  139 
differential,  142 
construction    and    gra- 
duation of,  141 
rules  for  translating  the 

degrees  of,  140 
manner  of  using,  141 
Thermo  metrograph,  142 
multiplicator,  142 


INDEX. 


481 


Tongs,  lamp,  161,  170 

furnace,  159 
Tools,  50 

Towels,  place  for,  49,  53 
Tralle's  beam,  96 
Transfer  of  gases,  271 
Trap,  bell  stench,  47 
Trituration,  79 
Trivet,  158 

Troughs,  pneumatic,  265 
water,  266 
mercury,  269 
Tube,Ker's,  135 
rack,  62 

holders,  176,  177 
rests,  178 

apparatus,  for  distillation  of  gases, 
253 
Tubes,  test,  308 

drying,  340 
U,  340 

chlorcalcium,  341 
washing,  367 
dropping,  106 
boiling  in,  308 
graduation  of,  131 
flexible,  216 
India  rubber,  216 
reduction,  219 
porcelain,  218 
metallic,  218 
iron,  218 
platinum,  219 
glass,  219 
sublimation  in,  226 
distillation  in,  240 
heated,  162 
reduction,  179 
manufacture  of,  465 
Welter's,  465 
glass  blown,  456 
cut,  459 
cemented,  460 
bent,  460 

closed  and  drawn  out,  461 
edges    of,   widened   and 
smoothed,  459 


U 


U  tubes,  340 
Universal  furnaces,  150 
Ure's  apparatus  for  sublimation,  230 
eudiometer,  429 


Ure's  water  bath,  181 
Uses  of  baths,  180 


Vacuum  produced,  324 
Vacuo,  evaporation  in,  324 
desiccation  in,  338 
distillation  in,  293 
Vapors,  specific  gravity  of  determined, 
122 

ignition  of  bodies  in,  202 
Varnish,  black,  58 
Ventilation,  26,  39 
Ventzke's  apparatus,  395 
Vessels,  coated  with  fire  lute,  278 
exhausted  of  air,  109 
graduated,  130 
cleansed,  48 
Volatile  liquids,  distillation  of,  249 

substances,    detection    of,    by 
blowpipe,  379 
Voltaic  pile,  431 
Voltameter,  Faraday's,  443 


W 


Washing,  363 

bottles,  356,  364,  384 

tubes,  367 

of    precipitates    and    filters, 

365 
by  decantation,  364 
Water,  constant  supply  of  hot,  41,  66 
for  the  laboratory,  49 
bath,  45,  181,  183 
distilled,  72 
trough,  266 

gases  collected  over,  268 
mother,  treatment  of,  330 
Weighing,  102 

directions  for,  103 
double,  104 
of  solids,  104 

hygrometric    substances, 

105 
corrosive  substances,  105 
liquids,  106 

volatUe,  108 
gases,  108 
Weights,  98 

metrical  or  decimal,  table  of, 


482 


INDEX. 


Weights,  avoirdupois,  61 

series  of,  for  analytic  balance, 

101 
adjudication  of,  100 
preservation  of,  101 

Welter's  tube,  manufacture  of,  465 

Wind  furnace,  154 

Wire,  for  battery  purposes,  440 

WolfFe's  bottles,  258 

Wollaston"s  blowpipe,  369 
battery,  432 


Work  bench,  50 
Writing  desk,  32 


Zinc,  granulation  of,  83 

local  action  on,  in  batteries,  433 
prevented  by  amal- 
gamation, 434 


THE    END. 


LABORATORY 


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